Not long ago JM posted a 1KHz sinewave oscillator with very low distortion. It used a 470uF non polarized capacitor which in practice would probably be made from two 1000uF capacitors.
There's nothing wrong with that but I wanted to see whether I could make a working circuit without needing such a large capacitor.
What I have so far is below.
Any comments?
What's the best way to control the output level?
Currently it's 5v pk-pk but I rather have half that.
On 31/03/2025 5:54 am, Edward Rawde wrote:
Not long ago JM posted a 1KHz sinewave oscillator with very low distortion. >> It used a 470uF non polarized capacitor which in practice would probably be made from two 1000uF capacitors.
There's nothing wrong with that but I wanted to see whether I could make a working circuit without needing such a large
capacitor.
What I have so far is below.
Any comments?
It relies on the Analog Devices MAT-02 dual transistor, which is now obsolete
https://www.analog.com/media/en/technical-documentation/obsolete-data-sheets/mat02.pdf
The .asc file shows eight NPN transistors labelled MAT-02, presumably in four pairs of the part, but it isn't clear which of the
eight transistors should be paired up.
What's the best way to control the output level?
Currently it's 5v pk-pk but I rather have half that.
The rectified currents from the four phased shifted versions of of the output waveform flow through R13, R14, R15 and R16 into R11
and through it into the virtual earth set up at the inverting input of U3, where the summed current is compared with a fixed
current drawn from the +15V rail through D1 and R10.
Doubling R10 from 330k to 680k would roughly halve the output amplitude.
One could be more precise, but it wouudl be hard to justify the extra effort.
--
Bill Sloman, Sydney
"Bill Sloman" <[email protected]> wrote in message news:vsdi3h$3nagd$[email protected]...
On 31/03/2025 5:54 am, Edward Rawde wrote:
Not long ago JM posted a 1KHz sinewave oscillator with very low distortion. >>> It used a 470uF non polarized capacitor which in practice would probably be made from two 1000uF capacitors.
There's nothing wrong with that but I wanted to see whether I could make a working circuit without needing such a large
capacitor.
What I have so far is below.
Any comments?
It relies on the Analog Devices MAT-02 dual transistor, which is now obsolete
https://www.analog.com/media/en/technical-documentation/obsolete-data-sheets/mat02.pdf
The .asc file shows eight NPN transistors labelled MAT-02, presumably in four pairs of the part, but it isn't clear which of the
eight transistors should be paired up.
BCM61B is available and very reasonably priced. https://www.digikey.ca/en/products/detail/nexperia-usa-inc/BCM61B-215/2119400 It can be used for Q1 Q2 and Q3 Q4 in the circuit below.
The remaining four transistors can use MAT14 https://www.digikey.be/en/products/detail/analog-devices-inc/MAT14ARZ-R7/2510588
which although a bit pricey has four independent matched transistors.
I can't find an LTSpice model for MAT14 so MAT02 is still shown in the circuit below.
What's the best way to control the output level?
Currently it's 5v pk-pk but I rather have half that.
The rectified currents from the four phased shifted versions of of the output waveform flow through R13, R14, R15 and R16 into R11
and through it into the virtual earth set up at the inverting input of U3, where the summed current is compared with a fixed
current drawn from the +15V rail through D1 and R10.
Doubling R10 from 330k to 680k would roughly halve the output amplitude.
One could be more precise, but it wouudl be hard to justify the extra effort.
Ah yes, that takes care of the output level.
The revised circuit is below.
Line 459 will need to be unwrapped.
On 1/04/2025 2:09 pm, Edward Rawde wrote:
"Bill Sloman" <[email protected]> wrote in message news:vsdi3h$3nagd$[email protected]...
On 31/03/2025 5:54 am, Edward Rawde wrote:
Not long ago JM posted a 1KHz sinewave oscillator with very low distortion.
It used a 470uF non polarized capacitor which in practice would probably be made from two 1000uF capacitors.
There's nothing wrong with that but I wanted to see whether I could make a working circuit without needing such a large
capacitor.
What I have so far is below.
Any comments?
It relies on the Analog Devices MAT-02 dual transistor, which is now obsolete
https://www.analog.com/media/en/technical-documentation/obsolete-data-sheets/mat02.pdf
The .asc file shows eight NPN transistors labelled MAT-02, presumably in four pairs of the part, but it isn't clear which of the
eight transistors should be paired up.
BCM61B is available and very reasonably priced.
https://www.digikey.ca/en/products/detail/nexperia-usa-inc/BCM61B-215/2119400
It can be used for Q1 Q2 and Q3 Q4 in the circuit below.
The remaining four transistors can use MAT14
https://www.digikey.be/en/products/detail/analog-devices-inc/MAT14ARZ-R7/2510588
which although a bit pricey has four independent matched transistors.
I can't find an LTSpice model for MAT14 so MAT02 is still shown in the circuit below.
What's the best way to control the output level?
Currently it's 5v pk-pk but I rather have half that.
The rectified currents from the four phased shifted versions of of the output waveform flow through R13, R14, R15 and R16 into
R11
and through it into the virtual earth set up at the inverting input of U3, where the summed current is compared with a fixed
current drawn from the +15V rail through D1 and R10.
Doubling R10 from 330k to 680k would roughly halve the output amplitude. >>> One could be more precise, but it wouudl be hard to justify the extra effort.
Ah yes, that takes care of the output level.
Not all that well. Using the positive rail as your voltage reference suck, and including the diode drops of the rectifying diodes
is even worse.There are precision rectifiers that use op amps to take out the diode drop, and synchromous rectifiers built around
transmission gates can be even more precise.
The revised circuit is below.
Line 459 will need to be unwrapped.
I did that, and the circuit does work, after a fashion.
It still uses eight transistors to do what John May did with three separate discrete transistors.
Because he didn't use a matched pair, he had to use two 250R emitter resistors to get the operating conditions he needed to make
them act as parts of a three-transistor asymmetric Wilson current mirror.
https://en.wikipedia.org/wiki/Wilson_current_mirror
He then had to by-pass the resistors with a big capacitor to get the effect he needed. This introduced a phase shift, but John
May's phase-shift oscillator offers four different phases from which he could pick off the right phase to get the correction
signal he needed.
By summing current from two adjacent phases you can get exactly the phase shift you need, but he didn't to be all that exact.
Using a matched pair for the two transistors at the bottom of the mirror you can get rid of one of the emitter resistors and make
the other one small enough not to matter (so you don't need the capacitor), but you do need to pick off a different phase to get
the right feedback.
The MAT04 is totally unnecessary.
Or it least that's the way it strikes me. I've yet to get a simulation to work to illustrate the point - it's a complicated
circuit, and once it hits saturation the subtle effects that stabilise it get swamped.
I need a better grasp of what's going on in the circuit, and a way to start it up that doesn't let it slide over into saturation
before it stabilises.
--
Bill Sloman, Sydney
Not long ago JM posted a 1KHz sinewave oscillator with very low distortion. >It used a 470uF non polarized capacitor which in practice would probably be made from two 1000uF capacitors.
There's nothing wrong with that but I wanted to see whether I could make a working circuit without needing such a large capacitor.
What I have so far is below.
Any comments?
On Sun, 30 Mar 2025 14:54:56 -0400, "Edward Rawde"
<[email protected]d> wrote:
Not long ago JM posted a 1KHz sinewave oscillator with very low distortion. >> It used a 470uF non polarized capacitor which in practice would probably be made from two 1000uF capacitors.
There's nothing wrong with that but I wanted to see whether I could make a working circuit without needing such a large capacitor.
What I have so far is below.
Any comments?
What's the best way to control the output level?
Currently it's 5v pk-pk but I rather have half that.
You'd be as well omitting Q1, Q2, Q11 and Q12. Just tie R17 toI made those changes to Edward Rawde's original circuit, and the revised circuit worked. I haven't yet got a clue how, but poking around in a
Q7e(Q8b) with other end to vee, and R28 to Q6e(Q9b) (adjust polarity
of gain vontrol voltage). There will be no loss in performance. Q6-9
are within an overall control loop, and there is no need for matched transistors (within reason).
If you splash out on a matched quad it would be better used to
construct a four quadrant multiplier, it would have lower harmonics
than this circuit if done correctly.
Are the one ohm resistors used for some sort of simulation/measurement purpose?
On Sun, 30 Mar 2025 14:54:56 -0400, "Edward Rawde"
<[email protected]d> wrote:
Not long ago JM posted a 1KHz sinewave oscillator with very low distortion. >> It used a 470uF non polarized capacitor which in practice would probably be made from two 1000uF capacitors.
There's nothing wrong with that but I wanted to see whether I could make a working circuit without needing such a large capacitor.
What I have so far is below.
Any comments?
Suppose you built an oscillator and had a switch that varied the loop
gain between 0.98 and 1.02. Now measure the amplitude of N cycles and
flip the switch if it's too high or too low. Switch at the zero
crossing.
I wonder what distortion would be like.
(I wouldn't really do that. It's just an idea to play with.)
On 4/04/2025 4:02 am, john larkin wrote:
On Sun, 30 Mar 2025 14:54:56 -0400, "Edward Rawde"
<[email protected]d> wrote:
Not long ago JM posted a 1KHz sinewave oscillator with very low distortion. >>> It used a 470uF non polarized capacitor which in practice would probably be made from two 1000uF capacitors.
There's nothing wrong with that but I wanted to see whether I could make a working circuit without needing such a large capacitor.
What I have so far is below.
Any comments?
Suppose you built an oscillator and had a switch that varied the loop
gain between 0.98 and 1.02. Now measure the amplitude of N cycles and
flip the switch if it's too high or too low. Switch at the zero
crossing.
I wonder what distortion would be like.
Why not measure it? LTSpice could probably give you a sine wave whose >amplitude ramped up linearly for a bit, and ramped back down again.
Do a DFT on that and you'd have your answer. It wouldn't be good.
(I wouldn't really do that. It's just an idea to play with.)
Only if you don't know what you are talking about.
On Sun, 30 Mar 2025 14:54:56 -0400, "Edward Rawde"...
<[email protected]d> wrote:
Not long ago JM posted a 1KHz sinewave oscillator with very low distortion. >>It used a 470uF non polarized capacitor which in practice would probably be made from two 1000uF capacitors.
There's nothing wrong with that but I wanted to see whether I could make a working circuit without needing such a large capacitor.
What I have so far is below.
Any comments?
What's the best way to control the output level?
Currently it's 5v pk-pk but I rather have half that.
You'd be as well omitting Q1, Q2, Q11 and Q12. Just tie R17 to
Q7e(Q8b) with other end to vee, and R28 to Q6e(Q9b) (adjust polarity
of gain vontrol voltage). There will be no loss in performance. Q6-9
are within an overall control loop, and there is no need for matched transistors (wthin reason).
If you splash out on a matched quad it would be better used to
construct a four quadrant multiplier, it would have lower harmonics
than this circuit if done correctly.
Are the one ohm resistors used for some sort of simulation/measurement purpose?
On Fri, 4 Apr 2025 05:14:44 +1100, Bill Sloman <[email protected]>
wrote:
On 4/04/2025 4:02 am, john larkin wrote:
On Sun, 30 Mar 2025 14:54:56 -0400, "Edward Rawde"
<[email protected]d> wrote:
Not long ago JM posted a 1KHz sinewave oscillator with very low distortion.
It used a 470uF non polarized capacitor which in practice would probably be made from two 1000uF capacitors.
There's nothing wrong with that but I wanted to see whether I could make a working circuit without needing such a large capacitor.
What I have so far is below.
Any comments?
Suppose you built an oscillator and had a switch that varied the loop
gain between 0.98 and 1.02. Now measure the amplitude of N cycles and
flip the switch if it's too high or too low. Switch at the zero
crossing.
I wonder what distortion would be like.
Why not measure it? LTSpice could probably give you a sine wave whose
amplitude ramped up linearly for a bit, and ramped back down again.
Do a DFT on that and you'd have your answer. It wouldn't be good.
(I wouldn't really do that. It's just an idea to play with.)
Only if you don't know what you are talking about.
An idea is like a cute baby puppy. Some people want to feed it and
play with it and some people want to club it to death.
On Thu, 3 Apr 2025 19:25:33 -0400, "Edward Rawde"
<[email protected]d> wrote:
"JM" <[email protected]> wrote in message news:[email protected]...
On Sun, 30 Mar 2025 14:54:56 -0400, "Edward Rawde"
<[email protected]d> wrote:
Not long ago JM posted a 1KHz sinewave oscillator with very low distortion.
It used a 470uF non polarized capacitor which in practice would probably be made from two 1000uF capacitors.
There's nothing wrong with that but I wanted to see whether I could make a working circuit without needing such a large capacitor.
You will need to adjust the feedback to suit. Start with a -5 or -6
gain block after the integrator and adjust it's gain until the startup
is clean (no saturation).
On Fri, 4 Apr 2025 05:14:44 +1100, Bill Sloman <[email protected]>
wrote:
On 4/04/2025 4:02 am, john larkin wrote:
On Sun, 30 Mar 2025 14:54:56 -0400, "Edward Rawde"
<[email protected]d> wrote:
Not long ago JM posted a 1KHz sinewave oscillator with very low distortion.
It used a 470uF non polarized capacitor which in practice would probably be made from two 1000uF capacitors.
There's nothing wrong with that but I wanted to see whether I could make a working circuit without needing such a large capacitor.
What I have so far is below.
Any comments?
Suppose you built an oscillator and had a switch that varied the loop
gain between 0.98 and 1.02. Now measure the amplitude of N cycles and
flip the switch if it's too high or too low. Switch at the zero
crossing.
I wonder what distortion would be like.
Why not measure it? LTSpice could probably give you a sine wave whose >>amplitude ramped up linearly for a bit, and ramped back down again.
Do a DFT on that and you'd have your answer. It wouldn't be good.
(I wouldn't really do that. It's just an idea to play with.)
Only if you don't know what you are talking about.
An idea is like a cute baby puppy. Some people want to feed it and
play with it and some people want to club it to death.
On Thu, 03 Apr 2025 13:08:20 -0700, john larkin <[email protected]>
wrote:
On Fri, 4 Apr 2025 05:14:44 +1100, Bill Sloman <[email protected]> >>wrote:
On 4/04/2025 4:02 am, john larkin wrote:
On Sun, 30 Mar 2025 14:54:56 -0400, "Edward Rawde"
<[email protected]d> wrote:
Not long ago JM posted a 1KHz sinewave oscillator with very low distortion.
It used a 470uF non polarized capacitor which in practice would probably be made from two 1000uF capacitors.
There's nothing wrong with that but I wanted to see whether I could make a working circuit without needing such a large capacitor.
What I have so far is below.
Any comments?
Suppose you built an oscillator and had a switch that varied the loop
gain between 0.98 and 1.02. Now measure the amplitude of N cycles and
flip the switch if it's too high or too low. Switch at the zero
crossing.
I wonder what distortion would be like.
Why not measure it? LTSpice could probably give you a sine wave whose >>>amplitude ramped up linearly for a bit, and ramped back down again.
Do a DFT on that and you'd have your answer. It wouldn't be good.
(I wouldn't really do that. It's just an idea to play with.)
Only if you don't know what you are talking about.
An idea is like a cute baby puppy. Some people want to feed it and
play with it and some people want to club it to death.
"Please don't feed the troll."
"Bill Sloman" <[email protected]> wrote in message news:vsnufh$2ou7j$[email protected]...
On 4/04/2025 11:33 am, JM wrote:...
On Thu, 3 Apr 2025 19:25:33 -0400, "Edward Rawde"
<[email protected]d> wrote:
"JM" <[email protected]> wrote in message news:[email protected]...
On Sun, 30 Mar 2025 14:54:56 -0400, "Edward Rawde"
<[email protected]d> wrote:
Not long ago JM posted a 1KHz sinewave oscillator with very low distortion.
It used a 470uF non polarized capacitor which in practice would probably be made from two 1000uF capacitors.
There's nothing wrong with that but I wanted to see whether I could make a working circuit without needing such a large
capacitor.
You will need to adjust the feedback to suit. Start with a -5 or -6
gain block after the integrator and adjust it's gain until the startup
is clean (no saturation).
Here's my version of John May's variation.
On 4/04/2025 11:33 am, JM wrote:
On Thu, 3 Apr 2025 19:25:33 -0400, "Edward Rawde"
<[email protected]d> wrote:
"JM" <[email protected]> wrote in message news:[email protected]...
On Sun, 30 Mar 2025 14:54:56 -0400, "Edward Rawde"
<[email protected]d> wrote:
Not long ago JM posted a 1KHz sinewave oscillator with very low distortion.
It used a 470uF non polarized capacitor which in practice would probably be made from two 1000uF capacitors.
There's nothing wrong with that but I wanted to see whether I could make a working circuit without needing such a large
capacitor.
You will need to adjust the feedback to suit. Start with a -5 or -6
gain block after the integrator and adjust it's gain until the startup
is clean (no saturation).
Here's my version of John May's variation.
Linewraps are going to be a problem - delete all "\n" from the last few lines
On Fri, 4 Apr 2025 14:25:29 -0400, "Edward Rawde"
<[email protected]d> wrote:
"Bill Sloman" <[email protected]> wrote in message news:vsnufh$2ou7j$[email protected]...
On 4/04/2025 11:33 am, JM wrote:...
On Thu, 3 Apr 2025 19:25:33 -0400, "Edward Rawde"
<[email protected]d> wrote:
"JM" <[email protected]> wrote in message news:[email protected]...
On Sun, 30 Mar 2025 14:54:56 -0400, "Edward Rawde"
<[email protected]d> wrote:
Not long ago JM posted a 1KHz sinewave oscillator with very low distortion.
It used a 470uF non polarized capacitor which in practice would probably be made from two 1000uF capacitors.
There's nothing wrong with that but I wanted to see whether I could make a working circuit without needing such a large
capacitor.
You will need to adjust the feedback to suit. Start with a -5 or -6
gain block after the integrator and adjust it's gain until the startup >>>> is clean (no saturation).
Here's my version of John May's variation.
Yes, that works but only 120dB down at 4KHz.
I put the damping resistor back to 47k since I don't care what happens during the first few seonds as long as it happens.
If it's necessary to wait one minute for the purest tone, that's fine with me.
Linewraps are going to be a problem - delete all "\n" from the last few lines
You don't want to remove \n just remove the wraps.
BCM61B does not have two independent transistors.
So you probably want BCM847BS which has two independent matched transistors and a very low price at digikey, so may as well use
two
of them as shown below.
I took the model from >>https://github.com/peteut/spice-models/blob/master/nxp/complex_discretes/complex_discretes.txt
It should only be necessary to unwrap the last line of the following.
Don't remove \n just remove the wraps, you may need to use a horizontal scroll bar.
Version 4.1
Best to just offset the integrator output so the amplitude is brought
under control sooner.
On Fri, 04 Apr 2025 18:03:19 +0100, Cursitor Doom <[email protected]>
wrote:
On Thu, 03 Apr 2025 13:08:20 -0700, john larkin <[email protected]> >>wrote:
On Fri, 4 Apr 2025 05:14:44 +1100, Bill Sloman <[email protected]> >>>wrote:
On 4/04/2025 4:02 am, john larkin wrote:
On Sun, 30 Mar 2025 14:54:56 -0400, "Edward Rawde"
<[email protected]d> wrote:
Not long ago JM posted a 1KHz sinewave oscillator with very low distortion.
It used a 470uF non polarized capacitor which in practice would probably be made from two 1000uF capacitors.
There's nothing wrong with that but I wanted to see whether I could make a working circuit without needing such a large capacitor.
What I have so far is below.
Any comments?
Suppose you built an oscillator and had a switch that varied the loop >>>>> gain between 0.98 and 1.02. Now measure the amplitude of N cycles and >>>>> flip the switch if it's too high or too low. Switch at the zero
crossing.
I wonder what distortion would be like.
Why not measure it? LTSpice could probably give you a sine wave whose >>>>amplitude ramped up linearly for a bit, and ramped back down again.
Do a DFT on that and you'd have your answer. It wouldn't be good.
(I wouldn't really do that. It's just an idea to play with.)
Only if you don't know what you are talking about.
An idea is like a cute baby puppy. Some people want to feed it and
play with it and some people want to club it to death.
"Please don't feed the troll."
The point here is that some people, especially fatheads with advanced >degrees, are incapable of having ideas, and react by being hostile to
ideas and to people who have them.
Even goofy ideas sometimes evolve into great ideas, if they are not
murdered at birth.
Electronic design, if it's not a routine mechanical activity, is about
ideas.
On Fri, 04 Apr 2025 18:03:19 +0100, Cursitor Doom <[email protected]>
wrote:
On Thu, 03 Apr 2025 13:08:20 -0700, john larkin <[email protected]>
wrote:
On Fri, 4 Apr 2025 05:14:44 +1100, Bill Sloman <[email protected]>
wrote:
On 4/04/2025 4:02 am, john larkin wrote:
On Sun, 30 Mar 2025 14:54:56 -0400, "Edward Rawde"
<[email protected]d> wrote:
Not long ago JM posted a 1KHz sinewave oscillator with very low distortion.
It used a 470uF non polarized capacitor which in practice would probably be made from two 1000uF capacitors.
There's nothing wrong with that but I wanted to see whether I could make a working circuit without needing such a large capacitor.
What I have so far is below.
Any comments?
Suppose you built an oscillator and had a switch that varied the loop >>>>> gain between 0.98 and 1.02. Now measure the amplitude of N cycles and >>>>> flip the switch if it's too high or too low. Switch at the zero
crossing.
I wonder what distortion would be like.
Why not measure it? LTSpice could probably give you a sine wave whose
amplitude ramped up linearly for a bit, and ramped back down again.
Do a DFT on that and you'd have your answer. It wouldn't be good.
(I wouldn't really do that. It's just an idea to play with.)
Only if you don't know what you are talking about.
An idea is like a cute baby puppy. Some people want to feed it and
play with it and some people want to club it to death.
"Please don't feed the troll."
The point here is that some people, especially fatheads with advanced degrees, are incapable of having ideas, and react by being hostile to
ideas and to people who have them.
Even goofy ideas sometimes evolve into great ideas, if they are not
murdered at birth.
Electronic design, if it's not a routine mechanical activity, is about
ideas.
On Fri, 04 Apr 2025 11:32:49 -0700, john larkin <jlArbor.com> wrote:
On Fri, 04 Apr 2025 18:03:19 +0100, Cursitor Doom <[email protected]>
wrote:
On Thu, 03 Apr 2025 13:08:20 -0700, john larkin <[email protected]>
wrote:
On Fri, 4 Apr 2025 05:14:44 +1100, Bill Sloman <[email protected]>
wrote:
On 4/04/2025 4:02 am, john larkin wrote:
On Sun, 30 Mar 2025 14:54:56 -0400, "Edward Rawde"
<[email protected]d> wrote:
Not long ago JM posted a 1KHz sinewave oscillator with very low distortion.
It used a 470uF non polarized capacitor which in practice would probably be made from two 1000uF capacitors.
There's nothing wrong with that but I wanted to see whether I could make a working circuit without needing such a large capacitor.
What I have so far is below.
Any comments?
Suppose you built an oscillator and had a switch that varied the loop >>>>>> gain between 0.98 and 1.02. Now measure the amplitude of N cycles and >>>>>> flip the switch if it's too high or too low. Switch at the zero
crossing.
I wonder what distortion would be like.
Why not measure it? LTSpice could probably give you a sine wave whose >>>>> amplitude ramped up linearly for a bit, and ramped back down again.
Do a DFT on that and you'd have your answer. It wouldn't be good.
(I wouldn't really do that. It's just an idea to play with.)
Only if you don't know what you are talking about.
An idea is like a cute baby puppy. Some people want to feed it and
play with it and some people want to club it to death.
"Please don't feed the troll."
The point here is that some people, especially fatheads with advanced
degrees, are incapable of having ideas, and react by being hostile to
ideas and to people who have them.
Even goofy ideas sometimes evolve into great ideas, if they are not
murdered at birth.
Electronic design, if it's not a routine mechanical activity, is about
ideas.
Well, Win Hill always said it was more of an art than a science.
On 5/04/2025 5:32 am, john larkin wrote:
On Fri, 04 Apr 2025 18:03:19 +0100, Cursitor Doom <[email protected]>
wrote:
On Thu, 03 Apr 2025 13:08:20 -0700, john larkin <[email protected]>
wrote:
On Fri, 4 Apr 2025 05:14:44 +1100, Bill Sloman <[email protected]>
wrote:
On 4/04/2025 4:02 am, john larkin wrote:
On Sun, 30 Mar 2025 14:54:56 -0400, "Edward Rawde"
<[email protected]d> wrote:
Not long ago JM posted a 1KHz sinewave oscillator with very low distortion.
It used a 470uF non polarized capacitor which in practice would probably be made from two 1000uF capacitors.
There's nothing wrong with that but I wanted to see whether I could make a working circuit without needing such a large
capacitor.
What I have so far is below.
Any comments?
Suppose you built an oscillator and had a switch that varied the loop >>>>>> gain between 0.98 and 1.02. Now measure the amplitude of N cycles and >>>>>> flip the switch if it's too high or too low. Switch at the zero
crossing.
I wonder what distortion would be like.
Why not measure it? LTSpice could probably give you a sine wave whose >>>>> amplitude ramped up linearly for a bit, and ramped back down again.
Do a DFT on that and you'd have your answer. It wouldn't be good.
(I wouldn't really do that. It's just an idea to play with.)
Only if you don't know what you are talking about.
An idea is like a cute baby puppy. Some people want to feed it and
play with it and some people want to club it to death.
"Please don't feed the troll."
The point here is that some people, especially fatheads with advanced
degrees, are incapable of having ideas, and react by being hostile to
ideas and to people who have them.
I've got my name three patents, so I'm demonstrably capable of having ideas.
I am hostile to people who tout bad ideas.
Even goofy ideas sometimes evolve into great ideas, if they are not
murdered at birth.
That's what brainstorming is about, but some ideas are hopelessly goofy.
Electronic design, if it's not a routine mechanical activity, is about
ideas.
Practical ideas. Ideally practicable ideas.
--
Bill Sloman, Sydney
On Fri, 4 Apr 2025 16:29:27 -0400, "Edward Rawde"
<[email protected]d> wrote:
"JM" <[email protected]> wrote in message news:[email protected]...
On Fri, 4 Apr 2025 14:25:29 -0400, "Edward Rawde"
<[email protected]d> wrote:
"Bill Sloman" <[email protected]> wrote in message news:vsnufh$2ou7j$[email protected]...
On 4/04/2025 11:33 am, JM wrote:...
On Thu, 3 Apr 2025 19:25:33 -0400, "Edward Rawde"
<[email protected]d> wrote:
"JM" <[email protected]> wrote in message news:[email protected]...
On Sun, 30 Mar 2025 14:54:56 -0400, "Edward Rawde"
<[email protected]d> wrote:
Not long ago JM posted a 1KHz sinewave oscillator with very low distortion.
It used a 470uF non polarized capacitor which in practice would probably be made from two 1000uF capacitors.
There's nothing wrong with that but I wanted to see whether I could make a working circuit without needing such a large
capacitor.
You will need to adjust the feedback to suit. Start with a -5 or -6 >>>>>> gain block after the integrator and adjust it's gain until the startup >>>>>> is clean (no saturation).
Here's my version of John May's variation.
Yes, that works but only 120dB down at 4KHz.
I put the damping resistor back to 47k since I don't care what happens during the first few seonds as long as it happens.
If it's necessary to wait one minute for the purest tone, that's fine with me.
Linewraps are going to be a problem - delete all "\n" from the last few lines
You don't want to remove \n just remove the wraps.
BCM61B does not have two independent transistors.
So you probably want BCM847BS which has two independent matched transistors and a very low price at digikey, so may as well use
two
of them as shown below.
I took the model from >>>>https://github.com/peteut/spice-models/blob/master/nxp/complex_discretes/complex_discretes.txt
It should only be necessary to unwrap the last line of the following. >>>>Don't remove \n just remove the wraps, you may need to use a horizontal scroll bar.
Version 4.1
Best to just offset the integrator output so the amplitude is brought
under control sooner.
Wow. That has much lower distortion too.
If you just replace Q1,2 duals with a simple long tailed pair I think
you will get better performance.
"Bill Sloman" <[email protected]> wrote in message news:vsq3um$107nb$[email protected]...
On 5/04/2025 5:32 am, john larkin wrote:
On Fri, 04 Apr 2025 18:03:19 +0100, Cursitor Doom <[email protected]>
wrote:
On Thu, 03 Apr 2025 13:08:20 -0700, john larkin <[email protected]>
wrote:
On Fri, 4 Apr 2025 05:14:44 +1100, Bill Sloman <[email protected]> >>>>> wrote:
On 4/04/2025 4:02 am, john larkin wrote:
On Sun, 30 Mar 2025 14:54:56 -0400, "Edward Rawde"
<[email protected]d> wrote:
Not long ago JM posted a 1KHz sinewave oscillator with very low distortion.
It used a 470uF non polarized capacitor which in practice would probably be made from two 1000uF capacitors.
There's nothing wrong with that but I wanted to see whether I could make a working circuit without needing such a large
capacitor.
What I have so far is below.
Any comments?
Suppose you built an oscillator and had a switch that varied the loop >>>>>>> gain between 0.98 and 1.02. Now measure the amplitude of N cycles and >>>>>>> flip the switch if it's too high or too low. Switch at the zero
crossing.
I wonder what distortion would be like.
Why not measure it? LTSpice could probably give you a sine wave whose >>>>>> amplitude ramped up linearly for a bit, and ramped back down again. >>>>>>
Do a DFT on that and you'd have your answer. It wouldn't be good.
(I wouldn't really do that. It's just an idea to play with.)
Only if you don't know what you are talking about.
An idea is like a cute baby puppy. Some people want to feed it and
play with it and some people want to club it to death.
"Please don't feed the troll."
The point here is that some people, especially fatheads with advanced
degrees, are incapable of having ideas, and react by being hostile to
ideas and to people who have them.
I've got my name three patents, so I'm demonstrably capable of having ideas. >>
I am hostile to people who tout bad ideas.
Don't you think it would be better to just explain why you think an idea is bad Bill?
And also, if necessary, to just explain how and why you think it should be done.
Being hostile doesn't make you look good and it does the opposite of persuading others that their ideas are bad.
So why be hostile at all?
On Fri, 4 Apr 2025 16:29:27 -0400, "Edward Rawde"
<[email protected]d> wrote:
"JM" <[email protected]> wrote in message news:[email protected]...
On Fri, 4 Apr 2025 14:25:29 -0400, "Edward Rawde"
<[email protected]d> wrote:
"Bill Sloman" <[email protected]> wrote in message news:vsnufh$2ou7j$[email protected]...
On 4/04/2025 11:33 am, JM wrote:...
On Thu, 3 Apr 2025 19:25:33 -0400, "Edward Rawde"
<[email protected]d> wrote:
"JM" <[email protected]> wrote in message news:[email protected]...
On Sun, 30 Mar 2025 14:54:56 -0400, "Edward Rawde"
<[email protected]d> wrote:
Not long ago JM posted a 1KHz sinewave oscillator with very low distortion.
It used a 470uF non polarized capacitor which in practice would probably be made from two 1000uF capacitors.
There's nothing wrong with that but I wanted to see whether I could make a working circuit without needing such a large
capacitor.
You will need to adjust the feedback to suit. Start with a -5 or -6 >>>>>> gain block after the integrator and adjust it's gain until the startup >>>>>> is clean (no saturation).
Here's my version of John May's variation.
Yes, that works but only 120dB down at 4KHz.
I put the damping resistor back to 47k since I don't care what happens during the first few seonds as long as it happens.
If it's necessary to wait one minute for the purest tone, that's fine with me.
Linewraps are going to be a problem - delete all "\n" from the last few lines
You don't want to remove \n just remove the wraps.
BCM61B does not have two independent transistors.
So you probably want BCM847BS which has two independent matched transistors and a very low price at digikey, so may as well use
two
of them as shown below.
I took the model from
https://github.com/peteut/spice-models/blob/master/nxp/complex_discretes/complex_discretes.txt
It should only be necessary to unwrap the last line of the following.
Don't remove \n just remove the wraps, you may need to use a horizontal scroll bar.
Version 4.1
Best to just offset the integrator output so the amplitude is brought
under control sooner.
Wow. That has much lower distortion too.
If you just replace Q1,2 duals with a simple long tailed pair I think
you will get better performance.
On 5/04/2025 10:12 am, JM wrote:
On Fri, 4 Apr 2025 16:29:27 -0400, "Edward Rawde"
<[email protected]d> wrote:
"JM" <[email protected]> wrote in message news:[email protected]...
On Fri, 4 Apr 2025 14:25:29 -0400, "Edward Rawde"
<[email protected]d> wrote:
"Bill Sloman" <[email protected]> wrote in message news:vsnufh$2ou7j$[email protected]...
On 4/04/2025 11:33 am, JM wrote:...
On Thu, 3 Apr 2025 19:25:33 -0400, "Edward Rawde"
<[email protected]d> wrote:
"JM" <[email protected]> wrote in message news:[email protected]...
On Sun, 30 Mar 2025 14:54:56 -0400, "Edward Rawde"
<[email protected]d> wrote:
Not long ago JM posted a 1KHz sinewave oscillator with very low distortion.
It used a 470uF non polarized capacitor which in practice would probably be made from two 1000uF capacitors.
There's nothing wrong with that but I wanted to see whether I could make a working circuit without needing such a large
capacitor.
You will need to adjust the feedback to suit. Start with a -5 or -6 >>>>>>> gain block after the integrator and adjust it's gain until the startup >>>>>>> is clean (no saturation).
Here's my version of John May's variation.
Yes, that works but only 120dB down at 4KHz.
I put the damping resistor back to 47k since I don't care what happens during the first few seonds as long as it happens.
If it's necessary to wait one minute for the purest tone, that's fine with me.
Linewraps are going to be a problem - delete all "\n" from the last few lines
You don't want to remove \n just remove the wraps.
BCM61B does not have two independent transistors.
So you probably want BCM847BS which has two independent matched transistors and a very low price at digikey, so may as well
use
two
of them as shown below.
I took the model from
https://github.com/peteut/spice-models/blob/master/nxp/complex_discretes/complex_discretes.txt
It should only be necessary to unwrap the last line of the following. >>>>> Don't remove \n just remove the wraps, you may need to use a horizontal scroll bar.
Version 4.1
Best to just offset the integrator output so the amplitude is brought
under control sooner.
Wow. That has much lower distortion too.
If you just replace Q1,2 duals with a simple long tailed pair I think
you will get better performance.
I've reworked my version of the circuit to incorporate most of John May's changes. I really dislike the Zener diode at D3 and have
solved that particular problem in a different way. My updated version has a 4kHz spike at 150dB below the fundamental and all the
other harmonics are even lower.
I'm inclined to agree with the proposition that two dual transistors is an over-kill, but my attempts at getting a long-tailed
pair solution to work didn't get anywhere. I need to rip up a few more ill-founded schemes.
On 5/04/2025 1:48 pm, Edward Rawde wrote:
"Bill Sloman" <[email protected]> wrote in message news:vsq3um$107nb$[email protected]...
On 5/04/2025 5:32 am, john larkin wrote:
On Fri, 04 Apr 2025 18:03:19 +0100, Cursitor Doom <[email protected]>
wrote:
On Thu, 03 Apr 2025 13:08:20 -0700, john larkin <[email protected]> >>>>> wrote:
On Fri, 4 Apr 2025 05:14:44 +1100, Bill Sloman <[email protected]> >>>>>> wrote:
On 4/04/2025 4:02 am, john larkin wrote:
On Sun, 30 Mar 2025 14:54:56 -0400, "Edward Rawde"
<[email protected]d> wrote:
Not long ago JM posted a 1KHz sinewave oscillator with very low distortion.
It used a 470uF non polarized capacitor which in practice would probably be made from two 1000uF capacitors.
There's nothing wrong with that but I wanted to see whether I could make a working circuit without needing such a large
capacitor.
What I have so far is below.
Any comments?
Suppose you built an oscillator and had a switch that varied the loop >>>>>>>> gain between 0.98 and 1.02. Now measure the amplitude of N cycles and >>>>>>>> flip the switch if it's too high or too low. Switch at the zero >>>>>>>> crossing.
I wonder what distortion would be like.
Why not measure it? LTSpice could probably give you a sine wave whose >>>>>>> amplitude ramped up linearly for a bit, and ramped back down again. >>>>>>>
Do a DFT on that and you'd have your answer. It wouldn't be good. >>>>>>>
(I wouldn't really do that. It's just an idea to play with.)
Only if you don't know what you are talking about.
An idea is like a cute baby puppy. Some people want to feed it and >>>>>> play with it and some people want to club it to death.
"Please don't feed the troll."
The point here is that some people, especially fatheads with advanced
degrees, are incapable of having ideas, and react by being hostile to
ideas and to people who have them.
I've got my name three patents, so I'm demonstrably capable of having ideas.
I am hostile to people who tout bad ideas.
Don't you think it would be better to just explain why you think an idea is bad Bill?
I usually do.
And also, if necessary, to just explain how and why you think it should be done.
I have been known to do that. You should know - I've done it to you, here, and I'm about to do it to John May whom I really like
and approve of.
Being hostile doesn't make you look good and it does the opposite of persuading others that their ideas are bad.
Few people can ever be persuaded that their ideas are bad. John Larkin definitely isn't one of them.
So why be hostile at all?
The same mechanism that persuades people that their bad ideas aren't too bad allows them to gloss over any criticism that isn't
thoroughly explicit.
--
Bill Sloman, Sydney
On Fri, 4 Apr 2025 23:55:11 -0400, "Edward Rawde"
<[email protected]d> wrote:
"JM" <[email protected]> wrote in message news:[email protected]...
On Fri, 4 Apr 2025 16:29:27 -0400, "Edward Rawde"
<[email protected]d> wrote:
"JM" <[email protected]> wrote in message news:[email protected]...
On Fri, 4 Apr 2025 14:25:29 -0400, "Edward Rawde"
<[email protected]d> wrote:
"Bill Sloman" <[email protected]> wrote in message news:vsnufh$2ou7j$[email protected]...
On 4/04/2025 11:33 am, JM wrote:...
On Thu, 3 Apr 2025 19:25:33 -0400, "Edward Rawde"
<[email protected]d> wrote:
"JM" <[email protected]> wrote in message news:[email protected]...
On Sun, 30 Mar 2025 14:54:56 -0400, "Edward Rawde"
<[email protected]d> wrote:
Not long ago JM posted a 1KHz sinewave oscillator with very low distortion.
It used a 470uF non polarized capacitor which in practice would probably be made from two 1000uF capacitors.
There's nothing wrong with that but I wanted to see whether I could make a working circuit without needing such a large
capacitor.
You will need to adjust the feedback to suit. Start with a -5 or -6 >>>>>>>> gain block after the integrator and adjust it's gain until the startup >>>>>>>> is clean (no saturation).
Here's my version of John May's variation.
Yes, that works but only 120dB down at 4KHz.
I put the damping resistor back to 47k since I don't care what happens during the first few seonds as long as it happens.
If it's necessary to wait one minute for the purest tone, that's fine with me.
Linewraps are going to be a problem - delete all "\n" from the last few lines
You don't want to remove \n just remove the wraps.
BCM61B does not have two independent transistors.
So you probably want BCM847BS which has two independent matched transistors and a very low price at digikey, so may as well
use
two
of them as shown below.
I took the model from >>>>>>https://github.com/peteut/spice-models/blob/master/nxp/complex_discretes/complex_discretes.txt
It should only be necessary to unwrap the last line of the following. >>>>>>Don't remove \n just remove the wraps, you may need to use a horizontal scroll bar.
Version 4.1
Best to just offset the integrator output so the amplitude is brought >>>>> under control sooner.
Wow. That has much lower distortion too.
If you just replace Q1,2 duals with a simple long tailed pair I think
you will get better performance.
I'm not sure I understand how the multiplier could be implemented with just a long tailed pair.
Just modulate the tail current and select how much to steer to the
output by directly driving the bases rather than indirectly as in your circuit. The following link shows one example topology, and a four
quadrant differential I/O version. Compare the linearity of each of
them.
https://1drv.ms/u/c/1af24d72a509cd48/EWVCUG7-jFJMu7-01VczCRcBzEC9JPHrV45x7TOunN90Gg?e=GXbvX5
It could be used as shown here.
https://1drv.ms/u/c/1af24d72a509cd48/EVmMVrvUD15GutoR5nCJ7QEBSeZsHWpHudqR0b8XtTLMLw?e=HIV74I
For best performance use the multplier circuit with differential I/O.
There is already a suitable drive point at U1 in the circuit.
The derived circuit below doesn't seem to have any discernible distortion at all as far as I can tell in an LTSpice FFT.
Not until you get above about 100KHz where it's 160dB down.
Best to use the Hanning windows at these levels if you're not already
doing so.
"Bill Sloman" <[email protected]> wrote in message news:vsqfc3$1emr4$[email protected]...
On 5/04/2025 10:12 am, JM wrote:
On Fri, 4 Apr 2025 16:29:27 -0400, "Edward Rawde"
<[email protected]d> wrote:
"JM" <[email protected]> wrote in message news:[email protected]...
On Fri, 4 Apr 2025 14:25:29 -0400, "Edward Rawde"
<[email protected]d> wrote:
"Bill Sloman" <[email protected]> wrote in message news:vsnufh$2ou7j$[email protected]...
On 4/04/2025 11:33 am, JM wrote:...
On Thu, 3 Apr 2025 19:25:33 -0400, "Edward Rawde"
<[email protected]d> wrote:
"JM" <[email protected]> wrote in message news:[email protected]...
On Sun, 30 Mar 2025 14:54:56 -0400, "Edward Rawde"
<[email protected]d> wrote:
Not long ago JM posted a 1KHz sinewave oscillator with very low distortion.
It used a 470uF non polarized capacitor which in practice would probably be made from two 1000uF capacitors.
There's nothing wrong with that but I wanted to see whether I could make a working circuit without needing such a large
capacitor.
You will need to adjust the feedback to suit. Start with a -5 or -6 >>>>>>>> gain block after the integrator and adjust it's gain until the startup >>>>>>>> is clean (no saturation).
Here's my version of John May's variation.
Yes, that works but only 120dB down at 4KHz.
I put the damping resistor back to 47k since I don't care what happens during the first few seonds as long as it happens.
If it's necessary to wait one minute for the purest tone, that's fine with me.
Linewraps are going to be a problem - delete all "\n" from the last few lines
You don't want to remove \n just remove the wraps.
BCM61B does not have two independent transistors.
So you probably want BCM847BS which has two independent matched transistors and a very low price at digikey, so may as well
use
two
of them as shown below.
I took the model from
https://github.com/peteut/spice-models/blob/master/nxp/complex_discretes/complex_discretes.txt
It should only be necessary to unwrap the last line of the following. >>>>>> Don't remove \n just remove the wraps, you may need to use a horizontal scroll bar.
Version 4.1
Best to just offset the integrator output so the amplitude is brought >>>>> under control sooner.
Wow. That has much lower distortion too.
If you just replace Q1,2 duals with a simple long tailed pair I think
you will get better performance.
I've reworked my version of the circuit to incorporate most of John May's changes. I really dislike the Zener diode at D3 and have
solved that particular problem in a different way. My updated version has a 4kHz spike at 150dB below the fundamental and all the
other harmonics are even lower.
I'm inclined to agree with the proposition that two dual transistors is an over-kill, but my attempts at getting a long-tailed
pair solution to work didn't get anywhere. I need to rip up a few more ill-founded schemes.
Are you sure that's the correct circuit?
It looks very similar to a circuit you posted yesterday and LTSpice 24.1.5 says 125dB down at 4 KHz.
"Bill Sloman" <[email protected]> wrote in message news:vsqeh2$1emr4$[email protected]...
On 5/04/2025 1:48 pm, Edward Rawde wrote:
"Bill Sloman" <[email protected]> wrote in message news:vsq3um$107nb$[email protected]...
On 5/04/2025 5:32 am, john larkin wrote:
On Fri, 04 Apr 2025 18:03:19 +0100, Cursitor Doom <[email protected]> >>>>> wrote:
On Thu, 03 Apr 2025 13:08:20 -0700, john larkin <[email protected]> >>>>>> wrote:
On Fri, 4 Apr 2025 05:14:44 +1100, Bill Sloman <[email protected]> >>>>>>> wrote:
On 4/04/2025 4:02 am, john larkin wrote:
On Sun, 30 Mar 2025 14:54:56 -0400, "Edward Rawde"
<[email protected]d> wrote:
Not long ago JM posted a 1KHz sinewave oscillator with very low distortion.
It used a 470uF non polarized capacitor which in practice would probably be made from two 1000uF capacitors.
There's nothing wrong with that but I wanted to see whether I could make a working circuit without needing such a large
capacitor.
What I have so far is below.
Any comments?
Suppose you built an oscillator and had a switch that varied the loop >>>>>>>>> gain between 0.98 and 1.02. Now measure the amplitude of N cycles and >>>>>>>>> flip the switch if it's too high or too low. Switch at the zero >>>>>>>>> crossing.
I wonder what distortion would be like.
Why not measure it? LTSpice could probably give you a sine wave whose >>>>>>>> amplitude ramped up linearly for a bit, and ramped back down again. >>>>>>>>
Do a DFT on that and you'd have your answer. It wouldn't be good. >>>>>>>>
(I wouldn't really do that. It's just an idea to play with.)
Only if you don't know what you are talking about.
An idea is like a cute baby puppy. Some people want to feed it and >>>>>>> play with it and some people want to club it to death.
"Please don't feed the troll."
The point here is that some people, especially fatheads with advanced >>>>> degrees, are incapable of having ideas, and react by being hostile to >>>>> ideas and to people who have them.
I've got my name three patents, so I'm demonstrably capable of having ideas.
I am hostile to people who tout bad ideas.
Don't you think it would be better to just explain why you think an idea is bad Bill?
I usually do.
And also, if necessary, to just explain how and why you think it should be done.
I have been known to do that. You should know - I've done it to you, here, and I'm about to do it to John May whom I really like
and approve of.
Being hostile doesn't make you look good and it does the opposite of persuading others that their ideas are bad.
Few people can ever be persuaded that their ideas are bad. John Larkin definitely isn't one of them.
So why be hostile at all?
The same mechanism that persuades people that their bad ideas aren't too bad allows them to gloss over any criticism that isn't
thoroughly explicit.
You can be critical without being hostile.
On Fri, 4 Apr 2025 23:55:11 -0400, "Edward Rawde"
<[email protected]d> wrote:
"JM" <[email protected]> wrote in message news:[email protected]...
On Fri, 4 Apr 2025 16:29:27 -0400, "Edward Rawde"
<[email protected]d> wrote:
"JM" <[email protected]> wrote in message news:[email protected]...
On Fri, 4 Apr 2025 14:25:29 -0400, "Edward Rawde"
<[email protected]d> wrote:
"Bill Sloman" <[email protected]> wrote in message news:vsnufh$2ou7j$[email protected]...
On 4/04/2025 11:33 am, JM wrote:...
On Thu, 3 Apr 2025 19:25:33 -0400, "Edward Rawde"
<[email protected]d> wrote:
"JM" <[email protected]> wrote in message news:[email protected]...
On Sun, 30 Mar 2025 14:54:56 -0400, "Edward Rawde"
<[email protected]d> wrote:
Not long ago JM posted a 1KHz sinewave oscillator with very low distortion.
It used a 470uF non polarized capacitor which in practice would probably be made from two 1000uF capacitors.
There's nothing wrong with that but I wanted to see whether I could make a working circuit without needing such a large
capacitor.
You will need to adjust the feedback to suit. Start with a -5 or -6 >>>>>>>> gain block after the integrator and adjust it's gain until the startup >>>>>>>> is clean (no saturation).
Here's my version of John May's variation.
Yes, that works but only 120dB down at 4KHz.
I put the damping resistor back to 47k since I don't care what happens during the first few seonds as long as it happens.
If it's necessary to wait one minute for the purest tone, that's fine with me.
Linewraps are going to be a problem - delete all "\n" from the last few lines
You don't want to remove \n just remove the wraps.
BCM61B does not have two independent transistors.
So you probably want BCM847BS which has two independent matched transistors and a very low price at digikey, so may as well
use
two
of them as shown below.
I took the model from >>>>>>https://github.com/peteut/spice-models/blob/master/nxp/complex_discretes/complex_discretes.txt
It should only be necessary to unwrap the last line of the following. >>>>>>Don't remove \n just remove the wraps, you may need to use a horizontal scroll bar.
Version 4.1
Best to just offset the integrator output so the amplitude is brought >>>>> under control sooner.
Wow. That has much lower distortion too.
If you just replace Q1,2 duals with a simple long tailed pair I think
you will get better performance.
I'm not sure I understand how the multiplier could be implemented with just a long tailed pair.
Just modulate the tail current and select how much to steer to the
output by directly driving the bases rather than indirectly as in your circuit. The following link shows one example topology, and a four
quadrant differential I/O version. Compare the linearity of each of
them.
https://1drv.ms/u/c/1af24d72a509cd48/EWVCUG7-jFJMu7-01VczCRcBzEC9JPHrV45x7TOunN90Gg?e=GXbvX5
It could be used as shown here.
https://1drv.ms/u/c/1af24d72a509cd48/EVmMVrvUD15GutoR5nCJ7QEBSeZsHWpHudqR0b8XtTLMLw?e=HIV74I
For best performance use the multplier circuit with differential I/O.
There is already a suitable drive point at U1 in the circuit.
The derived circuit below doesn't seem to have any discernible distortion at all as far as I can tell in an LTSpice FFT.
Not until you get above about 100KHz where it's 160dB down.
Best to use the Hanning windows at these levels if you're not already
doing so.
On Fri, 4 Apr 2025 23:55:11 -0400, "Edward Rawde"
<[email protected]d> wrote:
"JM" <[email protected]> wrote in message news:[email protected]...
On Fri, 4 Apr 2025 16:29:27 -0400, "Edward Rawde"
<[email protected]d> wrote:
"JM" <[email protected]> wrote in message news:[email protected]...
On Fri, 4 Apr 2025 14:25:29 -0400, "Edward Rawde"
<[email protected]d> wrote:
"Bill Sloman" <[email protected]> wrote in message news:vsnufh$2ou7j$[email protected]...
On 4/04/2025 11:33 am, JM wrote:...
On Thu, 3 Apr 2025 19:25:33 -0400, "Edward Rawde"
<[email protected]d> wrote:
"JM" <[email protected]> wrote in message news:[email protected]...
On Sun, 30 Mar 2025 14:54:56 -0400, "Edward Rawde"
<[email protected]d> wrote:
Not long ago JM posted a 1KHz sinewave oscillator with very low distortion.
It used a 470uF non polarized capacitor which in practice would probably be made from two 1000uF capacitors.
There's nothing wrong with that but I wanted to see whether I could make a working circuit without needing such a large
capacitor.
You will need to adjust the feedback to suit. Start with a -5 or -6 >>>>>>>> gain block after the integrator and adjust it's gain until the startup >>>>>>>> is clean (no saturation).
Here's my version of John May's variation.
Yes, that works but only 120dB down at 4KHz.
I put the damping resistor back to 47k since I don't care what happens during the first few seonds as long as it happens.
If it's necessary to wait one minute for the purest tone, that's fine with me.
Linewraps are going to be a problem - delete all "\n" from the last few lines
You don't want to remove \n just remove the wraps.
BCM61B does not have two independent transistors.
So you probably want BCM847BS which has two independent matched transistors and a very low price at digikey, so may as well use
two
of them as shown below.
I took the model from
https://github.com/peteut/spice-models/blob/master/nxp/complex_discretes/complex_discretes.txt
It should only be necessary to unwrap the last line of the following. >>>>>> Don't remove \n just remove the wraps, you may need to use a horizontal scroll bar.
Version 4.1
Best to just offset the integrator output so the amplitude is brought >>>>> under control sooner.
Wow. That has much lower distortion too.
If you just replace Q1,2 duals with a simple long tailed pair I think
you will get better performance.
I'm not sure I understand how the multiplier could be implemented with just a long tailed pair.
Just modulate the tail current and select how much to steer to the
output by directly driving the bases rather than indirectly as in your circuit. The following link shows one example topology, and a four
quadrant differential I/O version. Compare the linearity of each of
them.
https://1drv.ms/u/c/1af24d72a509cd48/EWVCUG7-jFJMu7-01VczCRcBzEC9JPHrV45x7TOunN90Gg?e=GXbvX5
It could be used as shown here.
https://1drv.ms/u/c/1af24d72a509cd48/EVmMVrvUD15GutoR5nCJ7QEBSeZsHWpHudqR0b8XtTLMLw?e=HIV74I
For best performance use the multiplier circuit with differential I/O.
There is already a suitable drive point at U1 in the circuit.
The derived circuit below doesn't seem to have any discernible distortion at all as far as I can tell in an LTSpice FFT.
Not until you get above about 100KHz where it's 160dB down.
Best to use the Hanning windows at these levels if you're not already
doing so.
On Fri, 4 Apr 2025 23:55:11 -0400, "Edward Rawde"
<[email protected]d> wrote:
"JM" <[email protected]> wrote in message news:[email protected]...
On Fri, 4 Apr 2025 16:29:27 -0400, "Edward Rawde"
<[email protected]d> wrote:
"JM" <[email protected]> wrote in message news:[email protected]...
On Fri, 4 Apr 2025 14:25:29 -0400, "Edward Rawde"
<[email protected]d> wrote:
"Bill Sloman" <[email protected]> wrote in message news:vsnufh$2ou7j$[email protected]...
On 4/04/2025 11:33 am, JM wrote:...
On Thu, 3 Apr 2025 19:25:33 -0400, "Edward Rawde"
<[email protected]d> wrote:
"JM" <[email protected]> wrote in message news:[email protected]...
On Sun, 30 Mar 2025 14:54:56 -0400, "Edward Rawde"
<[email protected]d> wrote:
Not long ago JM posted a 1KHz sinewave oscillator with very low distortion.
It used a 470uF non polarized capacitor which in practice would probably be made from two 1000uF capacitors.
There's nothing wrong with that but I wanted to see whether I could make a working circuit without needing such a large
capacitor.
You will need to adjust the feedback to suit. Start with a -5 or -6 >>>>>>>> gain block after the integrator and adjust it's gain until the startup >>>>>>>> is clean (no saturation).
Here's my version of John May's variation.
Yes, that works but only 120dB down at 4KHz.
I put the damping resistor back to 47k since I don't care what happens during the first few seonds as long as it happens.
If it's necessary to wait one minute for the purest tone, that's fine with me.
Linewraps are going to be a problem - delete all "\n" from the last few lines
You don't want to remove \n just remove the wraps.
BCM61B does not have two independent transistors.
So you probably want BCM847BS which has two independent matched transistors and a very low price at digikey, so may as well use
two
of them as shown below.
I took the model from
https://github.com/peteut/spice-models/blob/master/nxp/complex_discretes/complex_discretes.txt
It should only be necessary to unwrap the last line of the following. >>>>>> Don't remove \n just remove the wraps, you may need to use a horizontal scroll bar.
Version 4.1
Best to just offset the integrator output so the amplitude is brought >>>>> under control sooner.
Wow. That has much lower distortion too.
If you just replace Q1,2 duals with a simple long tailed pair I think
you will get better performance.
I'm not sure I understand how the multiplier could be implemented with just a long tailed pair.
Just modulate the tail current and select how much to steer to the
output by directly driving the bases rather than indirectly as in your circuit. The following link shows one example topology, and a four
quadrant differential I/O version. Compare the linearity of each of
them.
https://1drv.ms/u/c/1af24d72a509cd48/EWVCUG7-jFJMu7-01VczCRcBzEC9JPHrV45x7TOunN90Gg?e=GXbvX5
It could be used as shown here.
https://1drv.ms/u/c/1af24d72a509cd48/EVmMVrvUD15GutoR5nCJ7QEBSeZsHWpHudqR0b8XtTLMLw?e=HIV74I
On 6/04/2025 2:12 am, JM wrote:
On Fri, 4 Apr 2025 23:55:11 -0400, "Edward Rawde"
<[email protected]d> wrote:
"JM" <[email protected]> wrote in message news:[email protected]...
On Fri, 4 Apr 2025 16:29:27 -0400, "Edward Rawde"
<[email protected]d> wrote:
"JM" <[email protected]> wrote in message news:[email protected]...
On Fri, 4 Apr 2025 14:25:29 -0400, "Edward Rawde"
<[email protected]d> wrote:
"Bill Sloman" <[email protected]> wrote in message news:vsnufh$2ou7j$[email protected]...
On 4/04/2025 11:33 am, JM wrote:...
On Thu, 3 Apr 2025 19:25:33 -0400, "Edward Rawde"
<[email protected]d> wrote:
"JM" <[email protected]> wrote in message news:[email protected]...
On Sun, 30 Mar 2025 14:54:56 -0400, "Edward Rawde"
<[email protected]d> wrote:
Not long ago JM posted a 1KHz sinewave oscillator with very low distortion.
It used a 470uF non polarized capacitor which in practice would probably be made from two 1000uF capacitors.
There's nothing wrong with that but I wanted to see whether I could make a working circuit without needing such a large
capacitor.
You will need to adjust the feedback to suit. Start with a -5 or -6 >>>>>>>>> gain block after the integrator and adjust it's gain until the startup
is clean (no saturation).
Here's my version of John May's variation.
Yes, that works but only 120dB down at 4KHz.
I put the damping resistor back to 47k since I don't care what happens during the first few seonds as long as it happens.
If it's necessary to wait one minute for the purest tone, that's fine with me.
Linewraps are going to be a problem - delete all "\n" from the last few lines
You don't want to remove \n just remove the wraps.
BCM61B does not have two independent transistors.
So you probably want BCM847BS which has two independent matched transistors and a very low price at digikey, so may as well
use
two
of them as shown below.
I took the model from
https://github.com/peteut/spice-models/blob/master/nxp/complex_discretes/complex_discretes.txt
It should only be necessary to unwrap the last line of the following. >>>>>>> Don't remove \n just remove the wraps, you may need to use a horizontal scroll bar.
Version 4.1
Best to just offset the integrator output so the amplitude is brought >>>>>> under control sooner.
Wow. That has much lower distortion too.
If you just replace Q1,2 duals with a simple long tailed pair I think
you will get better performance.
I'm not sure I understand how the multiplier could be implemented with just a long tailed pair.
Just modulate the tail current and select how much to steer to the
output by directly driving the bases rather than indirectly as in your
circuit. The following link shows one example topology, and a four
quadrant differential I/O version. Compare the linearity of each of
them.
https://1drv.ms/u/c/1af24d72a509cd48/EWVCUG7-jFJMu7-01VczCRcBzEC9JPHrV45x7TOunN90Gg?e=GXbvX5
It could be used as shown here.
https://1drv.ms/u/c/1af24d72a509cd48/EVmMVrvUD15GutoR5nCJ7QEBSeZsHWpHudqR0b8XtTLMLw?e=HIV74I
As I've already said, I like it. I've played with it a bit.
The ON-Semiconductor NSS40301MDR2G NPN dual comes with a 2mV guaranteed maximum difference in base-emitter voltages (at the same
emitter current). Edward Rawde's Nexperia BCM61B dual part has matched current gain, but no guarantee on the Vbe. The Nexperia
BCM847BS does offer 2mV base-emitter matching, and would presumably work just as well.
Putting in the ON-Semiconductor dual means that your gain control circuit doesn't have to waste output swing coping with
part-to-part variation.
I've added a cascode transistor (Q1, it should be Q4) to minimise any Early effect distortion.
I've snipped out the op amp driving the base of Q3. Once you'd gone AC-coupled, it wasn't doing anything useful.
And I've put a string of eight diodes in series with R10. They nominally compensate for the temperature dependence introduced by
the four rectifier diodes D2, D12, D13 and D14. In this version of the circuit the rectifiers knock about 0.6 volts off a sine
wave that peaks at 3.8V, about a quarter of the 15V rail. I haven't run the numbers to fix the best number of diodes, but
something between six and eight looks okay.
The harmonics aren't great - most of them are about 90dB below the fundamental, but the seventh is only 85dB down.
"Bill Sloman" <[email protected]> wrote in message news:vsu092$14oc7$[email protected]...
On 6/04/2025 2:12 am, JM wrote:
On Fri, 4 Apr 2025 23:55:11 -0400, "Edward Rawde"
<[email protected]d> wrote:
"JM" <[email protected]> wrote in message news:[email protected]...
On Fri, 4 Apr 2025 16:29:27 -0400, "Edward Rawde"
<[email protected]d> wrote:
"JM" <[email protected]> wrote in message news:[email protected]...
On Fri, 4 Apr 2025 14:25:29 -0400, "Edward Rawde"
<[email protected]d> wrote:
"Bill Sloman" <[email protected]> wrote in message news:vsnufh$2ou7j$[email protected]...
On 4/04/2025 11:33 am, JM wrote:...
On Thu, 3 Apr 2025 19:25:33 -0400, "Edward Rawde"
<[email protected]d> wrote:
"JM" <[email protected]> wrote in message news:[email protected]...
On Sun, 30 Mar 2025 14:54:56 -0400, "Edward Rawde"
<[email protected]d> wrote:
Not long ago JM posted a 1KHz sinewave oscillator with very low distortion.
It used a 470uF non polarized capacitor which in practice would probably be made from two 1000uF capacitors.
There's nothing wrong with that but I wanted to see whether I could make a working circuit without needing such a large
capacitor.
You will need to adjust the feedback to suit. Start with a -5 or -6 >>>>>>>>>> gain block after the integrator and adjust it's gain until the startup
is clean (no saturation).
Here's my version of John May's variation.
Yes, that works but only 120dB down at 4KHz.
I put the damping resistor back to 47k since I don't care what happens during the first few seonds as long as it happens.
If it's necessary to wait one minute for the purest tone, that's fine with me.
Linewraps are going to be a problem - delete all "\n" from the last few lines
You don't want to remove \n just remove the wraps.
BCM61B does not have two independent transistors.
So you probably want BCM847BS which has two independent matched transistors and a very low price at digikey, so may as well
use
two
of them as shown below.
I took the model from
https://github.com/peteut/spice-models/blob/master/nxp/complex_discretes/complex_discretes.txt
It should only be necessary to unwrap the last line of the following. >>>>>>>> Don't remove \n just remove the wraps, you may need to use a horizontal scroll bar.
Version 4.1
Best to just offset the integrator output so the amplitude is brought >>>>>>> under control sooner.
Wow. That has much lower distortion too.
If you just replace Q1,2 duals with a simple long tailed pair I think >>>>> you will get better performance.
I'm not sure I understand how the multiplier could be implemented with just a long tailed pair.
Just modulate the tail current and select how much to steer to the
output by directly driving the bases rather than indirectly as in your
circuit. The following link shows one example topology, and a four
quadrant differential I/O version. Compare the linearity of each of
them.
https://1drv.ms/u/c/1af24d72a509cd48/EWVCUG7-jFJMu7-01VczCRcBzEC9JPHrV45x7TOunN90Gg?e=GXbvX5
It could be used as shown here.
https://1drv.ms/u/c/1af24d72a509cd48/EVmMVrvUD15GutoR5nCJ7QEBSeZsHWpHudqR0b8XtTLMLw?e=HIV74I
As I've already said, I like it. I've played with it a bit.
The ON-Semiconductor NSS40301MDR2G NPN dual comes with a 2mV guaranteed maximum difference in base-emitter voltages (at the same
emitter current). Edward Rawde's Nexperia BCM61B dual part has matched current gain, but no guarantee on the Vbe. The Nexperia
BCM847BS does offer 2mV base-emitter matching, and would presumably work just as well.
Putting in the ON-Semiconductor dual means that your gain control circuit doesn't have to waste output swing coping with
part-to-part variation.
I've added a cascode transistor (Q1, it should be Q4) to minimise any Early effect distortion.
I've snipped out the op amp driving the base of Q3. Once you'd gone AC-coupled, it wasn't doing anything useful.
And I've put a string of eight diodes in series with R10. They nominally compensate for the temperature dependence introduced by
the four rectifier diodes D2, D12, D13 and D14. In this version of the circuit the rectifiers knock about 0.6 volts off a sine
wave that peaks at 3.8V, about a quarter of the 15V rail. I haven't run the numbers to fix the best number of diodes, but
something between six and eight looks okay.
The harmonics aren't great - most of them are about 90dB below the fundamental, but the seventh is only 85dB down.
Not sure I see the point if it's only 80dB down Bill.
@ 7Khz in LTSPice 24.1.5
I can almost get that from a simple phase shift oscillator and a 1KHz tuned circuit.
The last time I included a diode string like that in one of my circuits (which I seem to recall had better than 80dB performance)
you told me it was nuts.
On 7/04/2025 12:39 am, Edward Rawde wrote:
"Bill Sloman" <[email protected]> wrote in message news:vsu092$14oc7$[email protected]...
On 6/04/2025 2:12 am, JM wrote:
On Fri, 4 Apr 2025 23:55:11 -0400, "Edward Rawde"
<[email protected]d> wrote:
"JM" <[email protected]> wrote in message news:[email protected]...
On Fri, 4 Apr 2025 16:29:27 -0400, "Edward Rawde"
<[email protected]d> wrote:
"JM" <[email protected]> wrote in message news:[email protected]...
On Fri, 4 Apr 2025 14:25:29 -0400, "Edward Rawde"
<[email protected]d> wrote:
"Bill Sloman" <[email protected]> wrote in message news:vsnufh$2ou7j$[email protected]...
On 4/04/2025 11:33 am, JM wrote:...
On Thu, 3 Apr 2025 19:25:33 -0400, "Edward Rawde"
<[email protected]d> wrote:
"JM" <[email protected]> wrote in message news:[email protected]...
On Sun, 30 Mar 2025 14:54:56 -0400, "Edward Rawde"
<[email protected]d> wrote:
Not long ago JM posted a 1KHz sinewave oscillator with very low distortion.
It used a 470uF non polarized capacitor which in practice would probably be made from two 1000uF capacitors.
There's nothing wrong with that but I wanted to see whether I could make a working circuit without needing such a
large
capacitor.
You will need to adjust the feedback to suit. Start with a -5 or -6
gain block after the integrator and adjust it's gain until the startup
is clean (no saturation).
Here's my version of John May's variation.
Yes, that works but only 120dB down at 4KHz.
I put the damping resistor back to 47k since I don't care what happens during the first few seonds as long as it happens.
If it's necessary to wait one minute for the purest tone, that's fine with me.
Linewraps are going to be a problem - delete all "\n" from the last few lines
You don't want to remove \n just remove the wraps.
BCM61B does not have two independent transistors.
So you probably want BCM847BS which has two independent matched transistors and a very low price at digikey, so may as
well
use
two
of them as shown below.
I took the model from
https://github.com/peteut/spice-models/blob/master/nxp/complex_discretes/complex_discretes.txt
It should only be necessary to unwrap the last line of the following. >>>>>>>>> Don't remove \n just remove the wraps, you may need to use a horizontal scroll bar.
Version 4.1
Best to just offset the integrator output so the amplitude is brought >>>>>>>> under control sooner.
Wow. That has much lower distortion too.
If you just replace Q1,2 duals with a simple long tailed pair I think >>>>>> you will get better performance.
I'm not sure I understand how the multiplier could be implemented with just a long tailed pair.
Just modulate the tail current and select how much to steer to the
output by directly driving the bases rather than indirectly as in your >>>> circuit. The following link shows one example topology, and a four
quadrant differential I/O version. Compare the linearity of each of
them.
https://1drv.ms/u/c/1af24d72a509cd48/EWVCUG7-jFJMu7-01VczCRcBzEC9JPHrV45x7TOunN90Gg?e=GXbvX5
It could be used as shown here.
https://1drv.ms/u/c/1af24d72a509cd48/EVmMVrvUD15GutoR5nCJ7QEBSeZsHWpHudqR0b8XtTLMLw?e=HIV74I
As I've already said, I like it. I've played with it a bit.
The ON-Semiconductor NSS40301MDR2G NPN dual comes with a 2mV guaranteed maximum difference in base-emitter voltages (at the same
emitter current). Edward Rawde's Nexperia BCM61B dual part has matched current gain, but no guarantee on the Vbe. The Nexperia
BCM847BS does offer 2mV base-emitter matching, and would presumably work just as well.
Putting in the ON-Semiconductor dual means that your gain control circuit doesn't have to waste output swing coping with
part-to-part variation.
I've added a cascode transistor (Q1, it should be Q4) to minimise any Early effect distortion.
I've snipped out the op amp driving the base of Q3. Once you'd gone AC-coupled, it wasn't doing anything useful.
And I've put a string of eight diodes in series with R10. They nominally compensate for the temperature dependence introduced by
the four rectifier diodes D2, D12, D13 and D14. In this version of the circuit the rectifiers knock about 0.6 volts off a sine
wave that peaks at 3.8V, about a quarter of the 15V rail. I haven't run the numbers to fix the best number of diodes, but
something between six and eight looks okay.
The harmonics aren't great - most of them are about 90dB below the fundamental, but the seventh is only 85dB down.
Not sure I see the point if it's only 80dB down Bill.
@ 7Khz in LTSPice 24.1.5
LTSpice isn't all that reliable as predictor of low level distortion. Having an armoury of different circuits to try when you
finally get around to building and testing something real may be useful.
I can almost get that from a simple phase shift oscillator and a 1KHz tuned circuit.
I'm sure that you think so. John Larkin thought that a bang-bang amplitude control was worth suggesting...
The last time I included a diode string like that in one of my circuits (which I seem to recall had better than 80dB performance)
you told me it was nuts.
It probably was. In this case there are better ways of getting a rectified output than a simple series diode - I've posted
circuits which incorporate precision rectifiers which get rid of the forward drop through the diode, and I've built circuits that
used synchronous rectifiers built around transmission gates where the output isn't shifted by a temperature dependent diode drop.
It went into a GaAs single crystal puller as a retrofit.
The main point of the diode string was as a satirical comment on that aspect of the design you posted, which probably counts as
being hostile, but I am hostile to ill-thought out designs, hard though it is to get the design time to sort them out.
I've got stuck with sorting out other peoples half-baked designs often enough, but only after my bosses had had their noses rubbed
in the unfortunate consequences.
--
Bill Sloman, Sydney
"Bill Sloman" <[email protected]> wrote in message news:vsuacb$1d4ec$[email protected]...
On 7/04/2025 12:39 am, Edward Rawde wrote:
"Bill Sloman" <[email protected]> wrote in message news:vsu092$14oc7$[email protected]...
On 6/04/2025 2:12 am, JM wrote:
On Fri, 4 Apr 2025 23:55:11 -0400, "Edward Rawde"
<[email protected]d> wrote:
"JM" <[email protected]> wrote in message news:[email protected]...
On Fri, 4 Apr 2025 16:29:27 -0400, "Edward Rawde"
<[email protected]d> wrote:
"JM" <[email protected]> wrote in message news:[email protected]...
On Fri, 4 Apr 2025 14:25:29 -0400, "Edward Rawde"
<[email protected]d> wrote:
"Bill Sloman" <[email protected]> wrote in message news:vsnufh$2ou7j$[email protected]...
On 4/04/2025 11:33 am, JM wrote:...
On Thu, 3 Apr 2025 19:25:33 -0400, "Edward Rawde"
<[email protected]d> wrote:
"JM" <[email protected]> wrote in message news:[email protected]...
On Sun, 30 Mar 2025 14:54:56 -0400, "Edward Rawde" >>>>>>>>>>>>>> <[email protected]d> wrote:
Not long ago JM posted a 1KHz sinewave oscillator with very low distortion.
It used a 470uF non polarized capacitor which in practice would probably be made from two 1000uF capacitors.
There's nothing wrong with that but I wanted to see whether I could make a working circuit without needing such a
large
capacitor.
You will need to adjust the feedback to suit. Start with a -5 or -6
gain block after the integrator and adjust it's gain until the startup
is clean (no saturation).
Here's my version of John May's variation.
Yes, that works but only 120dB down at 4KHz.
I put the damping resistor back to 47k since I don't care what happens during the first few seonds as long as it happens.
If it's necessary to wait one minute for the purest tone, that's fine with me.
Linewraps are going to be a problem - delete all "\n" from the last few lines
You don't want to remove \n just remove the wraps.
BCM61B does not have two independent transistors.
So you probably want BCM847BS which has two independent matched transistors and a very low price at digikey, so may as
well
use
two
of them as shown below.
I took the model from
https://github.com/peteut/spice-models/blob/master/nxp/complex_discretes/complex_discretes.txt
It should only be necessary to unwrap the last line of the following.
Don't remove \n just remove the wraps, you may need to use a horizontal scroll bar.
Version 4.1
Best to just offset the integrator output so the amplitude is brought >>>>>>>>> under control sooner.
Wow. That has much lower distortion too.
If you just replace Q1,2 duals with a simple long tailed pair I think >>>>>>> you will get better performance.
I'm not sure I understand how the multiplier could be implemented with just a long tailed pair.
Just modulate the tail current and select how much to steer to the
output by directly driving the bases rather than indirectly as in your >>>>> circuit. The following link shows one example topology, and a four
quadrant differential I/O version. Compare the linearity of each of >>>>> them.
https://1drv.ms/u/c/1af24d72a509cd48/EWVCUG7-jFJMu7-01VczCRcBzEC9JPHrV45x7TOunN90Gg?e=GXbvX5
It could be used as shown here.
https://1drv.ms/u/c/1af24d72a509cd48/EVmMVrvUD15GutoR5nCJ7QEBSeZsHWpHudqR0b8XtTLMLw?e=HIV74I
As I've already said, I like it. I've played with it a bit.
The ON-Semiconductor NSS40301MDR2G NPN dual comes with a 2mV guaranteed maximum difference in base-emitter voltages (at the same
emitter current). Edward Rawde's Nexperia BCM61B dual part has matched current gain, but no guarantee on the Vbe. The Nexperia
BCM847BS does offer 2mV base-emitter matching, and would presumably work just as well.
Putting in the ON-Semiconductor dual means that your gain control circuit doesn't have to waste output swing coping with
part-to-part variation.
I've added a cascode transistor (Q1, it should be Q4) to minimise any Early effect distortion.
I've snipped out the op amp driving the base of Q3. Once you'd gone AC-coupled, it wasn't doing anything useful.
And I've put a string of eight diodes in series with R10. They nominally compensate for the temperature dependence introduced by
the four rectifier diodes D2, D12, D13 and D14. In this version of the circuit the rectifiers knock about 0.6 volts off a sine
wave that peaks at 3.8V, about a quarter of the 15V rail. I haven't run the numbers to fix the best number of diodes, but
something between six and eight looks okay.
The harmonics aren't great - most of them are about 90dB below the fundamental, but the seventh is only 85dB down.
Not sure I see the point if it's only 80dB down Bill.
@ 7Khz in LTSPice 24.1.5
LTSpice isn't all that reliable as predictor of low level distortion. Having an armoury of different circuits to try when you
finally get around to building and testing something real may be useful.
I can almost get that from a simple phase shift oscillator and a 1KHz tuned circuit.
I'm sure that you think so. John Larkin thought that a bang-bang amplitude control was worth suggesting...
The last time I included a diode string like that in one of my circuits (which I seem to recall had better than 80dB performance)
you told me it was nuts.
It probably was. In this case there are better ways of getting a rectified output than a simple series diode - I've posted
circuits which incorporate precision rectifiers which get rid of the forward drop through the diode, and I've built circuits that
used synchronous rectifiers built around transmission gates where the output isn't shifted by a temperature dependent diode drop.
It went into a GaAs single crystal puller as a retrofit.
The main point of the diode string was as a satirical comment on that aspect of the design you posted, which probably counts as
being hostile, but I am hostile to ill-thought out designs, hard though it is to get the design time to sort them out.
I don't see anything particularly hostile there Bill. Just different points of view.
I've got stuck with sorting out other peoples half-baked designs often enough, but only after my bosses had had their noses rubbed
in the unfortunate consequences.
When I started work as a fresh graduate (but one who also had practical experience with everything from TV antenna systems in
hospitals to AY-3-8500 based games) I was amazed at some of the analogue circuit design blunders I encountered.
In one case I built a piece of custom test equipment which needed +15V and -15V. An available transformer had two suitable isolated
secondary windings so I just used two 7815 devices.
Only to be told by a more experienced "Designer" that connecting the output of a 7815 to ground would short it out and I had to use
7915 for that.....
On 7/04/2025 3:25 am, Edward Rawde wrote:
"Bill Sloman" <[email protected]> wrote in message news:vsuacb$1d4ec$[email protected]...
On 7/04/2025 12:39 am, Edward Rawde wrote:
"Bill Sloman" <[email protected]> wrote in message news:vsu092$14oc7$[email protected]...
On 6/04/2025 2:12 am, JM wrote:
On Fri, 4 Apr 2025 23:55:11 -0400, "Edward Rawde"
<[email protected]d> wrote:
"JM" <[email protected]> wrote in message news:[email protected]...
On Fri, 4 Apr 2025 16:29:27 -0400, "Edward Rawde"
<[email protected]d> wrote:
"JM" <[email protected]> wrote in message news:[email protected]...
On Fri, 4 Apr 2025 14:25:29 -0400, "Edward Rawde"
<[email protected]d> wrote:
"Bill Sloman" <[email protected]> wrote in message news:vsnufh$2ou7j$[email protected]...
On 4/04/2025 11:33 am, JM wrote:...
On Thu, 3 Apr 2025 19:25:33 -0400, "Edward Rawde"
<[email protected]d> wrote:
"JM" <[email protected]> wrote in message news:[email protected]...
On Sun, 30 Mar 2025 14:54:56 -0400, "Edward Rawde" >>>>>>>>>>>>>>> <[email protected]d> wrote:
Not long ago JM posted a 1KHz sinewave oscillator with very low distortion.
It used a 470uF non polarized capacitor which in practice would probably be made from two 1000uF capacitors.
There's nothing wrong with that but I wanted to see whether I could make a working circuit without needing such a
large
capacitor.
You will need to adjust the feedback to suit. Start with a -5 or -6
gain block after the integrator and adjust it's gain until the startup
is clean (no saturation).
Here's my version of John May's variation.
Yes, that works but only 120dB down at 4KHz.
I put the damping resistor back to 47k since I don't care what happens during the first few seonds as long as it
happens.
If it's necessary to wait one minute for the purest tone, that's fine with me.
Linewraps are going to be a problem - delete all "\n" from the last few lines
You don't want to remove \n just remove the wraps.
BCM61B does not have two independent transistors.
So you probably want BCM847BS which has two independent matched transistors and a very low price at digikey, so may as
well
use
two
of them as shown below.
I took the model from
https://github.com/peteut/spice-models/blob/master/nxp/complex_discretes/complex_discretes.txt
It should only be necessary to unwrap the last line of the following.
Don't remove \n just remove the wraps, you may need to use a horizontal scroll bar.
Version 4.1
Best to just offset the integrator output so the amplitude is brought
under control sooner.
Wow. That has much lower distortion too.
If you just replace Q1,2 duals with a simple long tailed pair I think >>>>>>>> you will get better performance.
I'm not sure I understand how the multiplier could be implemented with just a long tailed pair.
Just modulate the tail current and select how much to steer to the >>>>>> output by directly driving the bases rather than indirectly as in your >>>>>> circuit. The following link shows one example topology, and a four >>>>>> quadrant differential I/O version. Compare the linearity of each of >>>>>> them.
https://1drv.ms/u/c/1af24d72a509cd48/EWVCUG7-jFJMu7-01VczCRcBzEC9JPHrV45x7TOunN90Gg?e=GXbvX5
It could be used as shown here.
https://1drv.ms/u/c/1af24d72a509cd48/EVmMVrvUD15GutoR5nCJ7QEBSeZsHWpHudqR0b8XtTLMLw?e=HIV74I
As I've already said, I like it. I've played with it a bit.
The ON-Semiconductor NSS40301MDR2G NPN dual comes with a 2mV guaranteed maximum difference in base-emitter voltages (at the
same
emitter current). Edward Rawde's Nexperia BCM61B dual part has matched current gain, but no guarantee on the Vbe. The Nexperia
BCM847BS does offer 2mV base-emitter matching, and would presumably work just as well.
Putting in the ON-Semiconductor dual means that your gain control circuit doesn't have to waste output swing coping with
part-to-part variation.
I've added a cascode transistor (Q1, it should be Q4) to minimise any Early effect distortion.
I've snipped out the op amp driving the base of Q3. Once you'd gone AC-coupled, it wasn't doing anything useful.
And I've put a string of eight diodes in series with R10. They nominally compensate for the temperature dependence introduced
by
the four rectifier diodes D2, D12, D13 and D14. In this version of the circuit the rectifiers knock about 0.6 volts off a sine
wave that peaks at 3.8V, about a quarter of the 15V rail. I haven't run the numbers to fix the best number of diodes, but
something between six and eight looks okay.
The harmonics aren't great - most of them are about 90dB below the fundamental, but the seventh is only 85dB down.
Not sure I see the point if it's only 80dB down Bill.
@ 7Khz in LTSPice 24.1.5
LTSpice isn't all that reliable as predictor of low level distortion. Having an armoury of different circuits to try when you
finally get around to building and testing something real may be useful. >>>
I can almost get that from a simple phase shift oscillator and a 1KHz tuned circuit.
I'm sure that you think so. John Larkin thought that a bang-bang amplitude control was worth suggesting...
The last time I included a diode string like that in one of my circuits (which I seem to recall had better than 80dB
performance)
you told me it was nuts.
It probably was. In this case there are better ways of getting a rectified output than a simple series diode - I've posted
circuits which incorporate precision rectifiers which get rid of the forward drop through the diode, and I've built circuits
that
used synchronous rectifiers built around transmission gates where the output isn't shifted by a temperature dependent diode
drop.
It went into a GaAs single crystal puller as a retrofit.
The main point of the diode string was as a satirical comment on that aspect of the design you posted, which probably counts as
being hostile, but I am hostile to ill-thought out designs, hard though it is to get the design time to sort them out.
I don't see anything particularly hostile there Bill. Just different points of view.
I've got stuck with sorting out other peoples half-baked designs often enough, but only after my bosses had had their noses
rubbed
in the unfortunate consequences.
When I started work as a fresh graduate (but one who also had practical experience with everything from TV antenna systems in
hospitals to AY-3-8500 based games) I was amazed at some of the analogue circuit design blunders I encountered.
In one case I built a piece of custom test equipment which needed +15V and -15V. An available transformer had two suitable
isolated
secondary windings so I just used two 7815 devices.
Only to be told by a more experienced "Designer" that connecting the output of a 7815 to ground would short it out and I had to
use
7915 for that.....
What he should have said was the you were messing up the ground returns by hooking up the +15V output of the second 7815 to the 0V
rail.
He was avoiding spending a long time talking about grounding and shielding, which is a rather specialised subject.
In this particular thread your eight transistor is bonkers, but it
works - not that I can see how.
John May could see how it worked, and how it could be simplified to four transistors - and eventually down
to two matched pairs.
He doesn't like it, and prefers the single
long-tailed pair approach, despite the fact that LTSpice says it
offers poorer performance.
I like the long-tailed pair approach myself - I can see exactly how it works - but it's probably worth my time to work out exactly
how the four transistor circuit actually works, and why it seems to offer lower distortion in LTSpice simulations. It's not the
kind of project that anybody would fund, and the chance that I'd learn anything interesting is remote
, but I'm not swamped with work at the moment.
--
Bill Sloman, Sydney
"JM" <[email protected]> wrote in message news:[email protected]...
On Fri, 4 Apr 2025 23:55:11 -0400, "Edward Rawde"
<[email protected]d> wrote:
"JM" <[email protected]> wrote in message news:[email protected]...
On Fri, 4 Apr 2025 16:29:27 -0400, "Edward Rawde"
<[email protected]d> wrote:
"JM" <[email protected]> wrote in message news:[email protected]...
On Fri, 4 Apr 2025 14:25:29 -0400, "Edward Rawde"
<[email protected]d> wrote:
"Bill Sloman" <[email protected]> wrote in message news:vsnufh$2ou7j$[email protected]...
On 4/04/2025 11:33 am, JM wrote:
On Thu, 3 Apr 2025 19:25:33 -0400, "Edward Rawde"....
<[email protected]d> wrote:
"JM" <[email protected]> wrote in message news:[email protected]...
On Sun, 30 Mar 2025 14:54:56 -0400, "Edward Rawde"
<[email protected]d> wrote:
Not long ago JM posted a 1KHz sinewave oscillator with very low distortion.
It used a 470uF non polarized capacitor which in practice would probably be made from two 1000uF capacitors.
There's nothing wrong with that but I wanted to see whether I could make a working circuit without needing such a large
capacitor.
"Bill Sloman" <[email protected]> wrote in message news:vsvspr$33gdd$[email protected]...
On 7/04/2025 3:25 am, Edward Rawde wrote:
"Bill Sloman" <[email protected]> wrote in message news:vsuacb$1d4ec$[email protected]...
On 7/04/2025 12:39 am, Edward Rawde wrote:
"Bill Sloman" <[email protected]> wrote in message news:vsu092$14oc7$[email protected]...
On 6/04/2025 2:12 am, JM wrote:
On Fri, 4 Apr 2025 23:55:11 -0400, "Edward Rawde"
<[email protected]d> wrote:
"JM" <[email protected]> wrote in message news:[email protected]...
On Fri, 4 Apr 2025 16:29:27 -0400, "Edward Rawde"
<[email protected]d> wrote:
"JM" <[email protected]> wrote in message news:[email protected]...
On Fri, 4 Apr 2025 14:25:29 -0400, "Edward Rawde"
<[email protected]d> wrote:
"Bill Sloman" <[email protected]> wrote in message news:vsnufh$2ou7j$[email protected]...
On 4/04/2025 11:33 am, JM wrote:...
On Thu, 3 Apr 2025 19:25:33 -0400, "Edward Rawde"
<[email protected]d> wrote:
"JM" <[email protected]> wrote in message news:[email protected]...
On Sun, 30 Mar 2025 14:54:56 -0400, "Edward Rawde" >>>>>>>>>>>>>>>> <[email protected]d> wrote:
Not long ago JM posted a 1KHz sinewave oscillator with very low distortion.
It used a 470uF non polarized capacitor which in practice would probably be made from two 1000uF capacitors.
There's nothing wrong with that but I wanted to see whether I could make a working circuit without needing such a
large
capacitor.
You will need to adjust the feedback to suit. Start with a -5 or -6
gain block after the integrator and adjust it's gain until the startup
is clean (no saturation).
Here's my version of John May's variation.
Yes, that works but only 120dB down at 4KHz.
I put the damping resistor back to 47k since I don't care what happens during the first few seonds as long as it
happens.
If it's necessary to wait one minute for the purest tone, that's fine with me.
Linewraps are going to be a problem - delete all "\n" from the last few lines
You don't want to remove \n just remove the wraps.
BCM61B does not have two independent transistors.
So you probably want BCM847BS which has two independent matched transistors and a very low price at digikey, so may as
well
use
two
of them as shown below.
I took the model from
https://github.com/peteut/spice-models/blob/master/nxp/complex_discretes/complex_discretes.txt
It should only be necessary to unwrap the last line of the following.
Don't remove \n just remove the wraps, you may need to use a horizontal scroll bar.
Version 4.1
Best to just offset the integrator output so the amplitude is brought
under control sooner.
Wow. That has much lower distortion too.
If you just replace Q1,2 duals with a simple long tailed pair I think >>>>>>>>> you will get better performance.
I'm not sure I understand how the multiplier could be implemented with just a long tailed pair.
Just modulate the tail current and select how much to steer to the >>>>>>> output by directly driving the bases rather than indirectly as in your >>>>>>> circuit. The following link shows one example topology, and a four >>>>>>> quadrant differential I/O version. Compare the linearity of each of >>>>>>> them.
https://1drv.ms/u/c/1af24d72a509cd48/EWVCUG7-jFJMu7-01VczCRcBzEC9JPHrV45x7TOunN90Gg?e=GXbvX5
It could be used as shown here.
https://1drv.ms/u/c/1af24d72a509cd48/EVmMVrvUD15GutoR5nCJ7QEBSeZsHWpHudqR0b8XtTLMLw?e=HIV74I
As I've already said, I like it. I've played with it a bit.
The ON-Semiconductor NSS40301MDR2G NPN dual comes with a 2mV guaranteed maximum difference in base-emitter voltages (at the
same
emitter current). Edward Rawde's Nexperia BCM61B dual part has matched current gain, but no guarantee on the Vbe. The Nexperia
BCM847BS does offer 2mV base-emitter matching, and would presumably work just as well.
Putting in the ON-Semiconductor dual means that your gain control circuit doesn't have to waste output swing coping with
part-to-part variation.
I've added a cascode transistor (Q1, it should be Q4) to minimise any Early effect distortion.
I've snipped out the op amp driving the base of Q3. Once you'd gone AC-coupled, it wasn't doing anything useful.
And I've put a string of eight diodes in series with R10. They nominally compensate for the temperature dependence introduced
by
the four rectifier diodes D2, D12, D13 and D14. In this version of the circuit the rectifiers knock about 0.6 volts off a sine
wave that peaks at 3.8V, about a quarter of the 15V rail. I haven't run the numbers to fix the best number of diodes, but
something between six and eight looks okay.
The harmonics aren't great - most of them are about 90dB below the fundamental, but the seventh is only 85dB down.
Not sure I see the point if it's only 80dB down Bill.
@ 7Khz in LTSPice 24.1.5
LTSpice isn't all that reliable as predictor of low level distortion. Having an armoury of different circuits to try when you
finally get around to building and testing something real may be useful. >>>>
I can almost get that from a simple phase shift oscillator and a 1KHz tuned circuit.
I'm sure that you think so. John Larkin thought that a bang-bang amplitude control was worth suggesting...
The last time I included a diode string like that in one of my circuits (which I seem to recall had better than 80dB
performance)
you told me it was nuts.
It probably was. In this case there are better ways of getting a rectified output than a simple series diode - I've posted
circuits which incorporate precision rectifiers which get rid of the forward drop through the diode, and I've built circuits
that
used synchronous rectifiers built around transmission gates where the output isn't shifted by a temperature dependent diode
drop.
It went into a GaAs single crystal puller as a retrofit.
The main point of the diode string was as a satirical comment on that aspect of the design you posted, which probably counts as
being hostile, but I am hostile to ill-thought out designs, hard though it is to get the design time to sort them out.
I don't see anything particularly hostile there Bill. Just different points of view.
I've got stuck with sorting out other peoples half-baked designs often enough, but only after my bosses had had their noses
rubbed
in the unfortunate consequences.
When I started work as a fresh graduate (but one who also had practical experience with everything from TV antenna systems in
hospitals to AY-3-8500 based games) I was amazed at some of the analogue circuit design blunders I encountered.
In one case I built a piece of custom test equipment which needed +15V and -15V. An available transformer had two suitable
isolated
secondary windings so I just used two 7815 devices.
Only to be told by a more experienced "Designer" that connecting the output of a 7815 to ground would short it out and I had to
use
7915 for that.....
What he should have said was the you were messing up the ground returns by hooking up the +15V output of the second 7815 to the 0V
rail.
He was avoiding spending a long time talking about grounding and shielding, which is a rather specialised subject.
I see. Thank you for letting me know what he was thinking Bill.
Do you have some kind of time machine that you travel around in so you can have a better knowledge of what happened in a past
situation when compared with someone who was actually there at the time?
In this particular thread your eight transistor is bonkers, but it
works - not that I can see how.
Seems pretty obvious to me how it works Bill.
If I didn't know how it was intended to work then it almost certainly would not work.
I'm surprised that you can't see how it works.
John May could see how it worked, and how it could be simplified to four transistors - and eventually down
to two matched pairs.
You seem to be very good at knowing what other people can/could see Bill.
He doesn't like it, and prefers the single
long-tailed pair approach, despite the fact that LTSpice says it
offers poorer performance.
He provided three examples. All of which obviously work.
The best one from my point of view is the one with lowest distortion.
After all the goal, when I started looking into sinewave oscillators, was to see whether it's really necessary to use thermistors,
lamps, opto devices or FETs.
I like the long-tailed pair approach myself - I can see exactly how it works - but it's probably worth my time to work out exactly
how the four transistor circuit actually works, and why it seems to offer lower distortion in LTSpice simulations. It's not the
kind of project that anybody would fund, and the chance that I'd learn anything interesting is remote.
Ah well I'm sorry if you aren't likely to learn anything interesting Bill.
I've learned a lot and will continue to do so.
, but I'm not swamped with work at the moment.
There are other things I should be doing but analogue circuit design has a certain attraction, particularly when assisted by someone
as capable as JM.
On 7/04/2025 11:10 pm, Edward Rawde wrote:
"Bill Sloman" <[email protected]> wrote in message news:vsvspr$33gdd$[email protected]...
On 7/04/2025 3:25 am, Edward Rawde wrote:
"Bill Sloman" <[email protected]> wrote in message news:vsuacb$1d4ec$[email protected]...
On 7/04/2025 12:39 am, Edward Rawde wrote:
"Bill Sloman" <[email protected]> wrote in message news:vsu092$14oc7$[email protected]...
On 6/04/2025 2:12 am, JM wrote:
On Fri, 4 Apr 2025 23:55:11 -0400, "Edward Rawde"
<[email protected]d> wrote:
"JM" <[email protected]> wrote in message news:[email protected]...
On Fri, 4 Apr 2025 16:29:27 -0400, "Edward Rawde"
<[email protected]d> wrote:
"JM" <[email protected]> wrote in message news:[email protected]...
On Fri, 4 Apr 2025 14:25:29 -0400, "Edward Rawde"
<[email protected]d> wrote:
"Bill Sloman" <[email protected]> wrote in message news:vsnufh$2ou7j$[email protected]...
On 4/04/2025 11:33 am, JM wrote:...
On Thu, 3 Apr 2025 19:25:33 -0400, "Edward Rawde" >>>>>>>>>>>>>>> <[email protected]d> wrote:
"JM" <[email protected]> wrote in message news:[email protected]...
On Sun, 30 Mar 2025 14:54:56 -0400, "Edward Rawde" >>>>>>>>>>>>>>>>> <[email protected]d> wrote:
Not long ago JM posted a 1KHz sinewave oscillator with very low distortion.
It used a 470uF non polarized capacitor which in practice would probably be made from two 1000uF capacitors.
There's nothing wrong with that but I wanted to see whether I could make a working circuit without needing such a
large
capacitor.
You will need to adjust the feedback to suit. Start with a -5 or -6
gain block after the integrator and adjust it's gain until the startup
is clean (no saturation).
Here's my version of John May's variation.
Yes, that works but only 120dB down at 4KHz.
I put the damping resistor back to 47k since I don't care what happens during the first few seonds as long as it
happens.
If it's necessary to wait one minute for the purest tone, that's fine with me.
Linewraps are going to be a problem - delete all "\n" from the last few lines
You don't want to remove \n just remove the wraps.
BCM61B does not have two independent transistors.
So you probably want BCM847BS which has two independent matched transistors and a very low price at digikey, so may as
well
use
two
of them as shown below.
I took the model from
https://github.com/peteut/spice-models/blob/master/nxp/complex_discretes/complex_discretes.txt
It should only be necessary to unwrap the last line of the following.
Don't remove \n just remove the wraps, you may need to use a horizontal scroll bar.
Version 4.1
Best to just offset the integrator output so the amplitude is brought
under control sooner.
Wow. That has much lower distortion too.
If you just replace Q1,2 duals with a simple long tailed pair I think
you will get better performance.
I'm not sure I understand how the multiplier could be implemented with just a long tailed pair.
Just modulate the tail current and select how much to steer to the >>>>>>>> output by directly driving the bases rather than indirectly as in your >>>>>>>> circuit. The following link shows one example topology, and a four >>>>>>>> quadrant differential I/O version. Compare the linearity of each of >>>>>>>> them.
https://1drv.ms/u/c/1af24d72a509cd48/EWVCUG7-jFJMu7-01VczCRcBzEC9JPHrV45x7TOunN90Gg?e=GXbvX5
It could be used as shown here.
https://1drv.ms/u/c/1af24d72a509cd48/EVmMVrvUD15GutoR5nCJ7QEBSeZsHWpHudqR0b8XtTLMLw?e=HIV74I
As I've already said, I like it. I've played with it a bit.
The ON-Semiconductor NSS40301MDR2G NPN dual comes with a 2mV guaranteed maximum difference in base-emitter voltages (at the
same
emitter current). Edward Rawde's Nexperia BCM61B dual part has matched current gain, but no guarantee on the Vbe. The
Nexperia
BCM847BS does offer 2mV base-emitter matching, and would presumably work just as well.
Putting in the ON-Semiconductor dual means that your gain control circuit doesn't have to waste output swing coping with
part-to-part variation.
I've added a cascode transistor (Q1, it should be Q4) to minimise any Early effect distortion.
I've snipped out the op amp driving the base of Q3. Once you'd gone AC-coupled, it wasn't doing anything useful.
And I've put a string of eight diodes in series with R10. They nominally compensate for the temperature dependence
introduced
by
the four rectifier diodes D2, D12, D13 and D14. In this version of the circuit the rectifiers knock about 0.6 volts off a
sine
wave that peaks at 3.8V, about a quarter of the 15V rail. I haven't run the numbers to fix the best number of diodes, but
something between six and eight looks okay.
The harmonics aren't great - most of them are about 90dB below the fundamental, but the seventh is only 85dB down.
Not sure I see the point if it's only 80dB down Bill.
@ 7Khz in LTSPice 24.1.5
LTSpice isn't all that reliable as predictor of low level distortion. Having an armoury of different circuits to try when you
finally get around to building and testing something real may be useful. >>>>>
I can almost get that from a simple phase shift oscillator and a 1KHz tuned circuit.
I'm sure that you think so. John Larkin thought that a bang-bang amplitude control was worth suggesting...
The last time I included a diode string like that in one of my circuits (which I seem to recall had better than 80dB
performance)
you told me it was nuts.
It probably was. In this case there are better ways of getting a rectified output than a simple series diode - I've posted
circuits which incorporate precision rectifiers which get rid of the forward drop through the diode, and I've built circuits
that
used synchronous rectifiers built around transmission gates where the output isn't shifted by a temperature dependent diode
drop.
It went into a GaAs single crystal puller as a retrofit.
The main point of the diode string was as a satirical comment on that aspect of the design you posted, which probably counts
as
being hostile, but I am hostile to ill-thought out designs, hard though it is to get the design time to sort them out.
I don't see anything particularly hostile there Bill. Just different points of view.
I've got stuck with sorting out other peoples half-baked designs often enough, but only after my bosses had had their noses
rubbed
in the unfortunate consequences.
When I started work as a fresh graduate (but one who also had practical experience with everything from TV antenna systems in
hospitals to AY-3-8500 based games) I was amazed at some of the analogue circuit design blunders I encountered.
In one case I built a piece of custom test equipment which needed +15V and -15V. An available transformer had two suitable
isolated
secondary windings so I just used two 7815 devices.
Only to be told by a more experienced "Designer" that connecting the output of a 7815 to ground would short it out and I had to
use
7915 for that.....
What he should have said was the you were messing up the ground returns by hooking up the +15V output of the second 7815 to the
0V
rail.
He was avoiding spending a long time talking about grounding and shielding, which is a rather specialised subject.
I see. Thank you for letting me know what he was thinking Bill.
Do you have some kind of time machine that you travel around in so you can have a better knowledge of what happened in a past
situation when compared with someone who was actually there at the time?
In this particular thread your eight transistor is bonkers, but it
works - not that I can see how.
Seems pretty obvious to me how it works Bill.
But John May could take out half the transistors and produce a circuit that still worked.
And you haven't made any attempt to explain how it does work.
If I didn't know how it was intended to work then it almost certainly would not work.
And suspect that that there were a lot of variations that didn't work
I'm surprised that you can't see how it works.
I've got a rough idea, but not good enough to let me do anything interesting, or to write any kind of useful explanation of what
is going on. Writing that kind of explanation is usually a necessary part of getting a circuit into production.
Management needs it before they will spend the extra money on document the design for production, and the final test technicians
and service engineers need it make sure that the circuit works and to be able to fix it when it doesn't.
John May could see how it worked, and how it could be simplified to four transistors - and eventually down
to two matched pairs.
You seem to be very good at knowing what other people can/could see Bill.
It's a necessary engineering skill. See above.
He doesn't like it, and prefers the single
long-tailed pair approach, despite the fact that LTSpice says it
offers poorer performance.
He provided three examples. All of which obviously work.
The best one from my point of view is the one with lowest distortion.
Which you haven't measured on a real circuit yet. Since you don't seem to be all that sensitive to the risks from power supply
feedthrough, doing that might be painfully educational
After all the goal, when I started looking into sinewave oscillators, was to see whether it's really necessary to use
thermistors,
lamps, opto devices or FETs.
Have you come to a conclusion yet? As I seem to have mentioned before, it strikes me that the answer is that it's obvious
necessary.
I like the long-tailed pair approach myself - I can see exactly how it works - but it's probably worth my time to work out
exactly
how the four transistor circuit actually works, and why it seems to offer lower distortion in LTSpice simulations. It's not the
kind of project that anybody would fund, and the chance that I'd learn anything interesting is remote.
Ah well I'm sorry if you aren't likely to learn anything interesting Bill.
That's text-chopping.
I've learned a lot and will continue to do so.
We can hope.
, but I'm not swamped with work at the moment.
There are other things I should be doing but analogue circuit design has a certain attraction, particularly when assisted by
someone
as capable as JM.
I doubt if thinks that he is assisting you. Correcting is probably closer to the mark.
--
Bill Sloman, Sydney
"Bill Sloman" <[email protected]> wrote in message news:vsqeh2$1emr4$[email protected]...
On 5/04/2025 1:48 pm, Edward Rawde wrote:
"Bill Sloman" <[email protected]> wrote in message news:vsq3um$107nb$[email protected]...
On 5/04/2025 5:32 am, john larkin wrote:
On Fri, 04 Apr 2025 18:03:19 +0100, Cursitor Doom <[email protected]> >>>>> wrote:
On Thu, 03 Apr 2025 13:08:20 -0700, john larkin <[email protected]> >>>>>> wrote:
On Fri, 4 Apr 2025 05:14:44 +1100, Bill Sloman <[email protected]> >>>>>>> wrote:
On 4/04/2025 4:02 am, john larkin wrote:
On Sun, 30 Mar 2025 14:54:56 -0400, "Edward Rawde"
<[email protected]d> wrote:
Not long ago JM posted a 1KHz sinewave oscillator with very low distortion.
It used a 470uF non polarized capacitor which in practice would probably be made from two 1000uF capacitors.
There's nothing wrong with that but I wanted to see whether I could make a working circuit without needing such a large
capacitor.
What I have so far is below.
Any comments?
Suppose you built an oscillator and had a switch that varied the loop >>>>>>>>> gain between 0.98 and 1.02. Now measure the amplitude of N cycles and >>>>>>>>> flip the switch if it's too high or too low. Switch at the zero >>>>>>>>> crossing.
I wonder what distortion would be like.
Why not measure it? LTSpice could probably give you a sine wave whose >>>>>>>> amplitude ramped up linearly for a bit, and ramped back down again. >>>>>>>>
Do a DFT on that and you'd have your answer. It wouldn't be good. >>>>>>>>
(I wouldn't really do that. It's just an idea to play with.)
Only if you don't know what you are talking about.
An idea is like a cute baby puppy. Some people want to feed it and >>>>>>> play with it and some people want to club it to death.
"Please don't feed the troll."
The point here is that some people, especially fatheads with advanced >>>>> degrees, are incapable of having ideas, and react by being hostile to >>>>> ideas and to people who have them.
I've got my name three patents, so I'm demonstrably capable of having ideas.
I am hostile to people who tout bad ideas.
Don't you think it would be better to just explain why you think an idea is bad Bill?
I usually do.
And also, if necessary, to just explain how and why you think it should be done.
I have been known to do that. You should know - I've done it to you, here, and I'm about to do it to John May whom I really like
and approve of.
Being hostile doesn't make you look good and it does the opposite of persuading others that their ideas are bad.
Few people can ever be persuaded that their ideas are bad. John Larkin definitely isn't one of them.
So why be hostile at all?
The same mechanism that persuades people that their bad ideas aren't too bad allows them to gloss over any criticism that isn't
thoroughly explicit.
You can be critical without being hostile.
On Mon, 7 Apr 2025 22:46:13 -0400, "Edward Rawde"
<[email protected]d> wrote:
"Edward Rawde" <[email protected]d> wrote in message news:vsso97$1imi$[email protected]...
"JM" <[email protected]> wrote in message news:[email protected]...
On Fri, 4 Apr 2025 23:55:11 -0400, "Edward Rawde"
<[email protected]d> wrote:
"JM" <[email protected]> wrote in message news:[email protected]...
On Fri, 4 Apr 2025 16:29:27 -0400, "Edward Rawde"
<[email protected]d> wrote:
"JM" <[email protected]> wrote in message news:[email protected]...
On Fri, 4 Apr 2025 14:25:29 -0400, "Edward Rawde"
<[email protected]d> wrote:
"Bill Sloman" <[email protected]> wrote in message news:vsnufh$2ou7j$[email protected]...
On 4/04/2025 11:33 am, JM wrote:
On Thu, 3 Apr 2025 19:25:33 -0400, "Edward Rawde"....
<[email protected]d> wrote:
"JM" <[email protected]> wrote in message news:[email protected]...
On Sun, 30 Mar 2025 14:54:56 -0400, "Edward Rawde"
<[email protected]d> wrote:
Not long ago JM posted a 1KHz sinewave oscillator with very low distortion.
It used a 470uF non polarized capacitor which in practice would probably be made from two 1000uF capacitors.
There's nothing wrong with that but I wanted to see whether I could make a working circuit without needing such a
large
capacitor.
Here's an almost fully practical circuit except for the current sources and sinks.
I reversed the polarity of the control feedback and applied it to the inverting input of the first oscilllator stage, removed some
redundant capacitors, and added some filtering to the gain control
signal. Also altered some gain values to improve the dynamics (but
that still has to be addressed).
Most real world designs would use a sample and hold circuit to sample
the output at it's maximum point and use that to control the feedback, similar to the topology I think I posted a while ago. It might be
worthwhile looking at that.
On Tue, 8 Apr 2025 14:41:44 -0400, "Edward Rawde"
<[email protected]d> wrote:
"JM" <[email protected]> wrote in message news:[email protected]...
On Mon, 7 Apr 2025 22:46:13 -0400, "Edward Rawde"Thanks. That has the lowest distortion I've seen in a simulation so far.
<[email protected]d> wrote:
"Edward Rawde" <[email protected]d> wrote in message news:vsso97$1imi$[email protected]...
"JM" <[email protected]> wrote in message news:[email protected]...
On Fri, 4 Apr 2025 23:55:11 -0400, "Edward Rawde"
<[email protected]d> wrote:
"JM" <[email protected]> wrote in message news:[email protected]...
On Fri, 4 Apr 2025 16:29:27 -0400, "Edward Rawde"
<[email protected]d> wrote:
"JM" <[email protected]> wrote in message news:[email protected]...
On Fri, 4 Apr 2025 14:25:29 -0400, "Edward Rawde"
<[email protected]d> wrote:
"Bill Sloman" <[email protected]> wrote in message news:vsnufh$2ou7j$[email protected]...
On 4/04/2025 11:33 am, JM wrote:
On Thu, 3 Apr 2025 19:25:33 -0400, "Edward Rawde"....
<[email protected]d> wrote:
"JM" <[email protected]> wrote in message news:[email protected]...
On Sun, 30 Mar 2025 14:54:56 -0400, "Edward Rawde" >>>>>>>>>>>>>>> <[email protected]d> wrote:
Not long ago JM posted a 1KHz sinewave oscillator with very low distortion.
It used a 470uF non polarized capacitor which in practice would probably be made from two 1000uF capacitors.
There's nothing wrong with that but I wanted to see whether I could make a working circuit without needing such a
large
capacitor.
Here's an almost fully practical circuit except for the current sources and sinks.
I reversed the polarity of the control feedback and applied it to the
inverting input of the first oscilllator stage, removed some
redundant capacitors, and added some filtering to the gain control
signal. Also altered some gain values to improve the dynamics (but
that still has to be addressed).
Most real world designs would use a sample and hold circuit to sample
the output at it's maximum point and use that to control the feedback,
similar to the topology I think I posted a while ago. It might be
worthwhile looking at that.
I can't find the sample/hold circuit you mentioned, would you mind reposting it?
Thank you for your help with this. It is much appreciated.
I wouldn't have kept a copy. It would probably be overkill anyway,
for a fixed frequency, and if the dynamics are not an issue, what you
already have is more than adequate for any audio use case I can think
of. You'd probably be better off writing decent spice models for the
opamp parts you would actually use, and optimizing signal levels in
the cct as is. Buffering the rectifier parts improve things somewhat.
On Tue, 8 Apr 2025 14:41:44 -0400, "Edward Rawde"
<[email protected]d> wrote:
"JM" <[email protected]> wrote in message news:[email protected]...
On Mon, 7 Apr 2025 22:46:13 -0400, "Edward Rawde"Thanks. That has the lowest distortion I've seen in a simulation so far.
<[email protected]d> wrote:
"Edward Rawde" <[email protected]d> wrote in message news:vsso97$1imi$[email protected]...
"JM" <[email protected]> wrote in message news:[email protected]...
On Fri, 4 Apr 2025 23:55:11 -0400, "Edward Rawde"
<[email protected]d> wrote:
"JM" <[email protected]> wrote in message news:[email protected]...
On Fri, 4 Apr 2025 16:29:27 -0400, "Edward Rawde"
<[email protected]d> wrote:
"JM" <[email protected]> wrote in message news:[email protected]...
On Fri, 4 Apr 2025 14:25:29 -0400, "Edward Rawde"
<[email protected]d> wrote:
"Bill Sloman" <[email protected]> wrote in message news:vsnufh$2ou7j$[email protected]...
On 4/04/2025 11:33 am, JM wrote:
On Thu, 3 Apr 2025 19:25:33 -0400, "Edward Rawde"....
<[email protected]d> wrote:
"JM" <[email protected]> wrote in message news:[email protected]...
On Sun, 30 Mar 2025 14:54:56 -0400, "Edward Rawde" >>>>>>>>>>>>>>> <[email protected]d> wrote:
Not long ago JM posted a 1KHz sinewave oscillator with very low distortion.
It used a 470uF non polarized capacitor which in practice would probably be made from two 1000uF capacitors.
There's nothing wrong with that but I wanted to see whether I could make a working circuit without needing such a
large
capacitor.
Here's an almost fully practical circuit except for the current sources and sinks.
I reversed the polarity of the control feedback and applied it to the
inverting input of the first oscilllator stage, removed some
redundant capacitors, and added some filtering to the gain control
signal. Also altered some gain values to improve the dynamics (but
that still has to be addressed).
Most real world designs would use a sample and hold circuit to sample
the output at it's maximum point and use that to control the feedback,
similar to the topology I think I posted a while ago. It might be
worthwhile looking at that.
I can't find the sample/hold circuit you mentioned, would you mind reposting it?
Thank you for your help with this. It is much appreciated.
On Sat, 5 Apr 2025 10:15:27 -0400, "Edward Rawde"
<[email protected]d> wrote:
"Bill Sloman" <[email protected]> wrote in message news:vsqeh2$1emr4$[email protected]...
On 5/04/2025 1:48 pm, Edward Rawde wrote:
"Bill Sloman" <[email protected]> wrote in message news:vsq3um$107nb$[email protected]...
On 5/04/2025 5:32 am, john larkin wrote:
On Fri, 04 Apr 2025 18:03:19 +0100, Cursitor Doom <[email protected]> >>>>>> wrote:
On Thu, 03 Apr 2025 13:08:20 -0700, john larkin <[email protected]> >>>>>>> wrote:
On Fri, 4 Apr 2025 05:14:44 +1100, Bill Sloman <[email protected]> >>>>>>>> wrote:
On 4/04/2025 4:02 am, john larkin wrote:
On Sun, 30 Mar 2025 14:54:56 -0400, "Edward Rawde"
<[email protected]d> wrote:
Not long ago JM posted a 1KHz sinewave oscillator with very low distortion.
It used a 470uF non polarized capacitor which in practice would probably be made from two 1000uF capacitors.
There's nothing wrong with that but I wanted to see whether I could make a working circuit without needing such a large
capacitor.
What I have so far is below.
Any comments?
Suppose you built an oscillator and had a switch that varied the loop
gain between 0.98 and 1.02. Now measure the amplitude of N cycles and
flip the switch if it's too high or too low. Switch at the zero >>>>>>>>>> crossing.
I wonder what distortion would be like.
Why not measure it? LTSpice could probably give you a sine wave whose >>>>>>>>> amplitude ramped up linearly for a bit, and ramped back down again. >>>>>>>>>
Do a DFT on that and you'd have your answer. It wouldn't be good. >>>>>>>>>
(I wouldn't really do that. It's just an idea to play with.) >>>>>>>>>Only if you don't know what you are talking about.
An idea is like a cute baby puppy. Some people want to feed it and >>>>>>>> play with it and some people want to club it to death.
"Please don't feed the troll."
The point here is that some people, especially fatheads with advanced >>>>>> degrees, are incapable of having ideas, and react by being hostile to >>>>>> ideas and to people who have them.
I've got my name three patents, so I'm demonstrably capable of having ideas.
I am hostile to people who tout bad ideas.
Don't you think it would be better to just explain why you think an idea is bad Bill?
I usually do.
And also, if necessary, to just explain how and why you think it should be done.
I have been known to do that. You should know - I've done it to you, here, and I'm about to do it to John May whom I really like
and approve of.
Being hostile doesn't make you look good and it does the opposite of persuading others that their ideas are bad.
Few people can ever be persuaded that their ideas are bad. John Larkin definitely isn't one of them.
So why be hostile at all?
The same mechanism that persuades people that their bad ideas aren't too bad allows them to gloss over any criticism that isn't
thoroughly explicit.
You can be critical without being hostile.
He can't. He lives to be nasty.
The super low distortion oscillator thing is just another venue to
call people stupid. It's a Spice-as-game thing, totally unrealistic in
real life.
"Bill Sloman" <[email protected]> wrote in message news:vt2bck$1gmbm$[email protected]...
On 7/04/2025 11:10 pm, Edward Rawde wrote:
"Bill Sloman" <[email protected]> wrote in message news:vsvspr$33gdd$[email protected]...
On 7/04/2025 3:25 am, Edward Rawde wrote:
"Bill Sloman" <[email protected]> wrote in message news:vsuacb$1d4ec$[email protected]...
On 7/04/2025 12:39 am, Edward Rawde wrote:
"Bill Sloman" <[email protected]> wrote in message news:vsu092$14oc7$[email protected]...
On 6/04/2025 2:12 am, JM wrote:
On Fri, 4 Apr 2025 23:55:11 -0400, "Edward Rawde"
<[email protected]d> wrote:
"JM" <[email protected]> wrote in message news:[email protected]...
On Fri, 4 Apr 2025 16:29:27 -0400, "Edward Rawde"
<[email protected]d> wrote:
"JM" <[email protected]> wrote in message news:[email protected]...
On Fri, 4 Apr 2025 14:25:29 -0400, "Edward Rawde"
<[email protected]d> wrote:
"Bill Sloman" <[email protected]> wrote in message news:vsnufh$2ou7j$[email protected]...
On 4/04/2025 11:33 am, JM wrote:...
On Thu, 3 Apr 2025 19:25:33 -0400, "Edward Rawde" >>>>>>>>>>>>>>>> <[email protected]d> wrote:
"JM" <[email protected]> wrote in message news:[email protected]...
On Sun, 30 Mar 2025 14:54:56 -0400, "Edward Rawde" >>>>>>>>>>>>>>>>>> <[email protected]d> wrote:
Not long ago JM posted a 1KHz sinewave oscillator with very low distortion.
It used a 470uF non polarized capacitor which in practice would probably be made from two 1000uF capacitors.
There's nothing wrong with that but I wanted to see whether I could make a working circuit without needing such a
large
capacitor.
You will need to adjust the feedback to suit. Start with a -5 or -6
gain block after the integrator and adjust it's gain until the startup
is clean (no saturation).
Here's my version of John May's variation.
Yes, that works but only 120dB down at 4KHz.
I put the damping resistor back to 47k since I don't care what happens during the first few seonds as long as it
happens.
If it's necessary to wait one minute for the purest tone, that's fine with me.
Linewraps are going to be a problem - delete all "\n" from the last few lines
You don't want to remove \n just remove the wraps. >>>>>>>>>>>>>>
BCM61B does not have two independent transistors.
So you probably want BCM847BS which has two independent matched transistors and a very low price at digikey, so may as
well
use
two
of them as shown below.
I took the model from
https://github.com/peteut/spice-models/blob/master/nxp/complex_discretes/complex_discretes.txt
It should only be necessary to unwrap the last line of the following.
Don't remove \n just remove the wraps, you may need to use a horizontal scroll bar.
Version 4.1
Best to just offset the integrator output so the amplitude is brought
under control sooner.
Wow. That has much lower distortion too.
If you just replace Q1,2 duals with a simple long tailed pair I think
you will get better performance.
I'm not sure I understand how the multiplier could be implemented with just a long tailed pair.
Just modulate the tail current and select how much to steer to the >>>>>>>>> output by directly driving the bases rather than indirectly as in your
circuit. The following link shows one example topology, and a four >>>>>>>>> quadrant differential I/O version. Compare the linearity of each of >>>>>>>>> them.
https://1drv.ms/u/c/1af24d72a509cd48/EWVCUG7-jFJMu7-01VczCRcBzEC9JPHrV45x7TOunN90Gg?e=GXbvX5
It could be used as shown here.
https://1drv.ms/u/c/1af24d72a509cd48/EVmMVrvUD15GutoR5nCJ7QEBSeZsHWpHudqR0b8XtTLMLw?e=HIV74I
As I've already said, I like it. I've played with it a bit.
The ON-Semiconductor NSS40301MDR2G NPN dual comes with a 2mV guaranteed maximum difference in base-emitter voltages (at the
same
emitter current). Edward Rawde's Nexperia BCM61B dual part has matched current gain, but no guarantee on the Vbe. The
Nexperia
BCM847BS does offer 2mV base-emitter matching, and would presumably work just as well.
Putting in the ON-Semiconductor dual means that your gain control circuit doesn't have to waste output swing coping with
part-to-part variation.
I've added a cascode transistor (Q1, it should be Q4) to minimise any Early effect distortion.
I've snipped out the op amp driving the base of Q3. Once you'd gone AC-coupled, it wasn't doing anything useful.
And I've put a string of eight diodes in series with R10. They nominally compensate for the temperature dependence
introduced
by
the four rectifier diodes D2, D12, D13 and D14. In this version of the circuit the rectifiers knock about 0.6 volts off a
sine
wave that peaks at 3.8V, about a quarter of the 15V rail. I haven't run the numbers to fix the best number of diodes, but
something between six and eight looks okay.
The harmonics aren't great - most of them are about 90dB below the fundamental, but the seventh is only 85dB down.
Not sure I see the point if it's only 80dB down Bill.
@ 7Khz in LTSPice 24.1.5
LTSpice isn't all that reliable as predictor of low level distortion. Having an armoury of different circuits to try when you
finally get around to building and testing something real may be useful.
I can almost get that from a simple phase shift oscillator and a 1KHz tuned circuit.
I'm sure that you think so. John Larkin thought that a bang-bang amplitude control was worth suggesting...
The last time I included a diode string like that in one of my circuits (which I seem to recall had better than 80dB
performance)
you told me it was nuts.
It probably was. In this case there are better ways of getting a rectified output than a simple series diode - I've posted
circuits which incorporate precision rectifiers which get rid of the forward drop through the diode, and I've built circuits
that
used synchronous rectifiers built around transmission gates where the output isn't shifted by a temperature dependent diode
drop.
It went into a GaAs single crystal puller as a retrofit.
The main point of the diode string was as a satirical comment on that aspect of the design you posted, which probably counts
as
being hostile, but I am hostile to ill-thought out designs, hard though it is to get the design time to sort them out.
I don't see anything particularly hostile there Bill. Just different points of view.
I've got stuck with sorting out other peoples half-baked designs often enough, but only after my bosses had had their noses
rubbed
in the unfortunate consequences.
When I started work as a fresh graduate (but one who also had practical experience with everything from TV antenna systems in
hospitals to AY-3-8500 based games) I was amazed at some of the analogue circuit design blunders I encountered.
In one case I built a piece of custom test equipment which needed +15V and -15V. An available transformer had two suitable
isolated
secondary windings so I just used two 7815 devices.
Only to be told by a more experienced "Designer" that connecting the output of a 7815 to ground would short it out and I had to
use
7915 for that.....
What he should have said was the you were messing up the ground returns by hooking up the +15V output of the second 7815 to the
0V
rail.
He was avoiding spending a long time talking about grounding and shielding, which is a rather specialised subject.
I see. Thank you for letting me know what he was thinking Bill.
Do you have some kind of time machine that you travel around in so you can have a better knowledge of what happened in a past
situation when compared with someone who was actually there at the time? >>>
In this particular thread your eight transistor is bonkers, but it
works - not that I can see how.
Seems pretty obvious to me how it works Bill.
But John May could take out half the transistors and produce a circuit that still worked.
One reason for that is that a current source/sink can be approximated by a high value resistor so instead of using a current mirror
a single resistor is likely to work fine.
You might need to reverse the polarity of the voltage drive but there are many ways to do that in this circuit.
And you haven't made any attempt to explain how it does work.
As I pointed out some time ago, you never explain how your circuits work Bill.
It's like you just expect others to accept that you have superior knowledge. If you really could see what other people think then I think you might be surprised at the amount of laughter going on.
If I didn't know how it was intended to work then it almost certainly would not work.
And suspect that that there were a lot of variations that didn't work
You can suspect what you like but that's just another example of you twisting the world into something you would like it to be.
Anyone with any understanding of this circuit at all knows that a very basic explanation of how it works is that you need to
multiply the gain control level by a sample of the oscillator signal and feed the result back into the oscillator.
So if your signals are in the form of two currents which never change polarity then a one quadrant current multiplier should work
fine.
You might then do some research to see if you can find any examples of circuits which meet that requirement.
https://www.google.com/search?q=one+quadrant+analog+current+multiplier&udm=2
Much like you might refer to Horowitz/Hill to see if there are any relevant example circuits.
I'm surprised that you can't see how it works.
I've got a rough idea, but not good enough to let me do anything interesting, or to write any kind of useful explanation of what
is going on. Writing that kind of explanation is usually a necessary part of getting a circuit into production.
I've yet to see you write an explanation of how a circuit works Bill.
Instead I've only seen circuits using three or four times as many components as the last one JM posted in this thread and never any
better than 70dB.
Then you get upset when the rest of the world tries to tell you that although your circuit may have a few good ideas in it, it's
worthless from a meeting the requirements point of view.
Management needs it before they will spend the extra money on document the design for production, and the final test technicians
and service engineers need it make sure that the circuit works and to be able to fix it when it doesn't.
It's a necessary engineering skill. See above.John May could see how it worked, and how it could be simplified to four transistors - and eventually down
to two matched pairs.
You seem to be very good at knowing what other people can/could see Bill. >>
I prefer not to make any assumptions about what other people can or can't see.
Particularly when I know nothing at all about them other than what has been posted here.
He doesn't like it, and prefers the single
long-tailed pair approach, despite the fact that LTSpice says it
offers poorer performance.
He provided three examples. All of which obviously work.
The best one from my point of view is the one with lowest distortion.
Which you haven't measured on a real circuit yet. Since you don't seem to be all that sensitive to the risks from power supply
feedthrough, doing that might be painfully educational
Of course Bill. I have absolutely no doubt that you would take great delight in my pain.
And I have no doubt that you would not offer any meaningful assistance with the power supply design because you would rather watch
me suffer.
Offering assistance could reduce my suffering which wouldn't do at all.
I'd probably use 6V batteries arranged for +/- 18V for a first test of a circuit like this.
With some series components for filtering and to stay below LT1679 36V max.
After all the goal, when I started looking into sinewave oscillators, was to see whether it's really necessary to use
thermistors,
lamps, opto devices or FETs.
Have you come to a conclusion yet? As I seem to have mentioned before, it strikes me that the answer is that it's obvious
necessary.
What's obviously necessary Bill?
The last circuit JM posted has no measurable distortion worth mentioning that I can see.
That's text-chopping.I like the long-tailed pair approach myself - I can see exactly how it works - but it's probably worth my time to work out
exactly
how the four transistor circuit actually works, and why it seems to offer lower distortion in LTSpice simulations. It's not the
kind of project that anybody would fund, and the chance that I'd learn anything interesting is remote.
Ah well I'm sorry if you aren't likely to learn anything interesting Bill. >>
I've learned a lot and will continue to do so.
We can hope.
I'd translate that into "I hope you never learn anything so I can continue to tell you how stupid you are".
, but I'm not swamped with work at the moment.
There are other things I should be doing but analogue circuit design has a certain attraction, particularly when assisted by
someone
as capable as JM.
I doubt if thinks that he is assisting you. Correcting is probably closer to the mark.
Of course Bill.
https://www.youtube.com/watch?v=Z9t_KDGqOmE
I have no doubt that your own circuits never need to be corrected Bill.
Maybe that's why they are so unnecessarily complex.
If no-one can see how it works, no-one can correct it.
On 9/04/2025 1:56 am, Edward Rawde wrote:
"Bill Sloman" <[email protected]> wrote in message news:vt2bck$1gmbm$[email protected]...
On 7/04/2025 11:10 pm, Edward Rawde wrote:
"Bill Sloman" <[email protected]> wrote in message news:vsvspr$33gdd$[email protected]...
On 7/04/2025 3:25 am, Edward Rawde wrote:
"Bill Sloman" <[email protected]> wrote in message news:vsuacb$1d4ec$[email protected]...
On 7/04/2025 12:39 am, Edward Rawde wrote:
"Bill Sloman" <[email protected]> wrote in message news:vsu092$14oc7$[email protected]...
On 6/04/2025 2:12 am, JM wrote:
On Fri, 4 Apr 2025 23:55:11 -0400, "Edward Rawde"
<[email protected]d> wrote:
"JM" <[email protected]> wrote in message news:[email protected]...
On Fri, 4 Apr 2025 16:29:27 -0400, "Edward Rawde"
<[email protected]d> wrote:
"JM" <[email protected]> wrote in message news:[email protected]...
On Fri, 4 Apr 2025 14:25:29 -0400, "Edward Rawde"
<[email protected]d> wrote:
"Bill Sloman" <[email protected]> wrote in message news:vsnufh$2ou7j$[email protected]...
On 4/04/2025 11:33 am, JM wrote:...
On Thu, 3 Apr 2025 19:25:33 -0400, "Edward Rawde" >>>>>>>>>>>>>>>>> <[email protected]d> wrote:
"JM" <[email protected]> wrote in message news:[email protected]...
On Sun, 30 Mar 2025 14:54:56 -0400, "Edward Rawde" >>>>>>>>>>>>>>>>>>> <[email protected]d> wrote:
Not long ago JM posted a 1KHz sinewave oscillator with very low distortion.
It used a 470uF non polarized capacitor which in practice would probably be made from two 1000uF capacitors.
There's nothing wrong with that but I wanted to see whether I could make a working circuit without needing such
a
large
capacitor.
You will need to adjust the feedback to suit. Start with a -5 or -6
gain block after the integrator and adjust it's gain until the startup
is clean (no saturation).
Here's my version of John May's variation.
Yes, that works but only 120dB down at 4KHz.
I put the damping resistor back to 47k since I don't care what happens during the first few seonds as long as it
happens.
If it's necessary to wait one minute for the purest tone, that's fine with me.
Linewraps are going to be a problem - delete all "\n" from the last few lines
You don't want to remove \n just remove the wraps. >>>>>>>>>>>>>>>
BCM61B does not have two independent transistors. >>>>>>>>>>>>>>>
So you probably want BCM847BS which has two independent matched transistors and a very low price at digikey, so may
as
well
use
two
of them as shown below.
I took the model from
https://github.com/peteut/spice-models/blob/master/nxp/complex_discretes/complex_discretes.txt
It should only be necessary to unwrap the last line of the following.
Don't remove \n just remove the wraps, you may need to use a horizontal scroll bar.
Version 4.1
Best to just offset the integrator output so the amplitude is brought
under control sooner.
Wow. That has much lower distortion too.
If you just replace Q1,2 duals with a simple long tailed pair I think
you will get better performance.
I'm not sure I understand how the multiplier could be implemented with just a long tailed pair.
Just modulate the tail current and select how much to steer to the >>>>>>>>>> output by directly driving the bases rather than indirectly as in your
circuit. The following link shows one example topology, and a four >>>>>>>>>> quadrant differential I/O version. Compare the linearity of each of >>>>>>>>>> them.
https://1drv.ms/u/c/1af24d72a509cd48/EWVCUG7-jFJMu7-01VczCRcBzEC9JPHrV45x7TOunN90Gg?e=GXbvX5
It could be used as shown here.
https://1drv.ms/u/c/1af24d72a509cd48/EVmMVrvUD15GutoR5nCJ7QEBSeZsHWpHudqR0b8XtTLMLw?e=HIV74I
As I've already said, I like it. I've played with it a bit.
The ON-Semiconductor NSS40301MDR2G NPN dual comes with a 2mV guaranteed maximum difference in base-emitter voltages (at
the
same
emitter current). Edward Rawde's Nexperia BCM61B dual part has matched current gain, but no guarantee on the Vbe. The
Nexperia
BCM847BS does offer 2mV base-emitter matching, and would presumably work just as well.
Putting in the ON-Semiconductor dual means that your gain control circuit doesn't have to waste output swing coping with
part-to-part variation.
I've added a cascode transistor (Q1, it should be Q4) to minimise any Early effect distortion.
I've snipped out the op amp driving the base of Q3. Once you'd gone AC-coupled, it wasn't doing anything useful.
And I've put a string of eight diodes in series with R10. They nominally compensate for the temperature dependence
introduced
by
the four rectifier diodes D2, D12, D13 and D14. In this version of the circuit the rectifiers knock about 0.6 volts off a
sine
wave that peaks at 3.8V, about a quarter of the 15V rail. I haven't run the numbers to fix the best number of diodes, but
something between six and eight looks okay.
The harmonics aren't great - most of them are about 90dB below the fundamental, but the seventh is only 85dB down.
Not sure I see the point if it's only 80dB down Bill.
@ 7Khz in LTSPice 24.1.5
LTSpice isn't all that reliable as predictor of low level distortion. Having an armoury of different circuits to try when
you
finally get around to building and testing something real may be useful.
I can almost get that from a simple phase shift oscillator and a 1KHz tuned circuit.
I'm sure that you think so. John Larkin thought that a bang-bang amplitude control was worth suggesting...
The last time I included a diode string like that in one of my circuits (which I seem to recall had better than 80dB
performance)
you told me it was nuts.
It probably was. In this case there are better ways of getting a rectified output than a simple series diode - I've posted
circuits which incorporate precision rectifiers which get rid of the forward drop through the diode, and I've built circuits
that
used synchronous rectifiers built around transmission gates where the output isn't shifted by a temperature dependent diode
drop.
It went into a GaAs single crystal puller as a retrofit.
The main point of the diode string was as a satirical comment on that aspect of the design you posted, which probably counts
as
being hostile, but I am hostile to ill-thought out designs, hard though it is to get the design time to sort them out.
I don't see anything particularly hostile there Bill. Just different points of view.
I've got stuck with sorting out other peoples half-baked designs often enough, but only after my bosses had had their noses
rubbed
in the unfortunate consequences.
When I started work as a fresh graduate (but one who also had practical experience with everything from TV antenna systems in
hospitals to AY-3-8500 based games) I was amazed at some of the analogue circuit design blunders I encountered.
In one case I built a piece of custom test equipment which needed +15V and -15V. An available transformer had two suitable
isolated
secondary windings so I just used two 7815 devices.
Only to be told by a more experienced "Designer" that connecting the output of a 7815 to ground would short it out and I had
to
use
7915 for that.....
What he should have said was the you were messing up the ground returns by hooking up the +15V output of the second 7815 to
the
0V
rail.
He was avoiding spending a long time talking about grounding and shielding, which is a rather specialised subject.
I see. Thank you for letting me know what he was thinking Bill.
Do you have some kind of time machine that you travel around in so you can have a better knowledge of what happened in a past
situation when compared with someone who was actually there at the time? >>>>
In this particular thread your eight transistor is bonkers, but it
works - not that I can see how.
Seems pretty obvious to me how it works Bill.
But John May could take out half the transistors and produce a circuit that still worked.
One reason for that is that a current source/sink can be approximated by a high value resistor so instead of using a current
mirror
a single resistor is likely to work fine.
You might need to reverse the polarity of the voltage drive but there are many ways to do that in this circuit.
And you haven't made any attempt to explain how it does work.
As I pointed out some time ago, you never explain how your circuits work Bill.
It's like you just expect others to accept that you have superior knowledge. >> If you really could see what other people think then I think you might be surprised at the amount of laughter going on.
If I didn't know how it was intended to work then it almost certainly would not work.
And suspect that that there were a lot of variations that didn't work
You can suspect what you like but that's just another example of you twisting the world into something you would like it to be.
Anyone with any understanding of this circuit at all knows that a very basic explanation of how it works is that you need to
multiply the gain control level by a sample of the oscillator signal and feed the result back into the oscillator.
So if your signals are in the form of two currents which never change polarity then a one quadrant current multiplier should work
fine.
You might then do some research to see if you can find any examples of circuits which meet that requirement.
https://www.google.com/search?q=one+quadrant+analog+current+multiplier&udm=2 >>
Much like you might refer to Horowitz/Hill to see if there are any relevant example circuits.
I'm surprised that you can't see how it works.
I've got a rough idea, but not good enough to let me do anything interesting, or to write any kind of useful explanation of what
is going on. Writing that kind of explanation is usually a necessary part of getting a circuit into production.
I've yet to see you write an explanation of how a circuit works Bill.
Instead I've only seen circuits using three or four times as many components as the last one JM posted in this thread and never
any
better than 70dB.
Then you get upset when the rest of the world tries to tell you that although your circuit may have a few good ideas in it, it's
worthless from a meeting the requirements point of view.
Management needs it before they will spend the extra money on document the design for production, and the final test technicians
and service engineers need it make sure that the circuit works and to be able to fix it when it doesn't.
It's a necessary engineering skill. See above.John May could see how it worked, and how it could be simplified to four transistors - and eventually down
to two matched pairs.
You seem to be very good at knowing what other people can/could see Bill. >>>
I prefer not to make any assumptions about what other people can or can't see.
Particularly when I know nothing at all about them other than what has been posted here.
He doesn't like it, and prefers the single
long-tailed pair approach, despite the fact that LTSpice says it
offers poorer performance.
He provided three examples. All of which obviously work.
The best one from my point of view is the one with lowest distortion.
Which you haven't measured on a real circuit yet. Since you don't seem to be all that sensitive to the risks from power supply
feedthrough, doing that might be painfully educational
Of course Bill. I have absolutely no doubt that you would take great delight in my pain.
And I have no doubt that you would not offer any meaningful assistance with the power supply design because you would rather
watch
me suffer.
Offering assistance could reduce my suffering which wouldn't do at all.
I'd probably use 6V batteries arranged for +/- 18V for a first test of a circuit like this.
With some series components for filtering and to stay below LT1679 36V max. >>
After all the goal, when I started looking into sinewave oscillators, was to see whether it's really necessary to use
thermistors,
lamps, opto devices or FETs.
Have you come to a conclusion yet? As I seem to have mentioned before, it strikes me that the answer is that it's obvious
necessary.
What's obviously necessary Bill?
The last circuit JM posted has no measurable distortion worth mentioning that I can see.
That's text-chopping.I like the long-tailed pair approach myself - I can see exactly how it works - but it's probably worth my time to work out
exactly
how the four transistor circuit actually works, and why it seems to offer lower distortion in LTSpice simulations. It's not
the
kind of project that anybody would fund, and the chance that I'd learn anything interesting is remote.
Ah well I'm sorry if you aren't likely to learn anything interesting Bill. >>>
I've learned a lot and will continue to do so.
We can hope.
I'd translate that into "I hope you never learn anything so I can continue to tell you how stupid you are".
That is a remarkably hostile reaction. Most engineers can eventually learn stuff, but some are slower at it than others.
Encouraging the slower ones takes quite a lot of effort because you have to go into quite a lot of detail before you can get the
message across,
and it can get tedious, and isn't all that rewarding. I'd love to be able to congratulate you for your insights, but they've been
a bit thin on the ground.
, but I'm not swamped with work at the moment.
There are other things I should be doing but analogue circuit design has a certain attraction, particularly when assisted by
someone
as capable as JM.
I doubt if thinks that he is assisting you. Correcting is probably closer to the mark.
Of course Bill.
https://www.youtube.com/watch?v=Z9t_KDGqOmE
I have no doubt that your own circuits never need to be corrected Bill.
You must be joking. I've had some very clever colleagues who could do it fast. There's at least one case where I didn't spot my
error until years later - the original solution worked fine but I eventually realised that there was a simpler way of getting
there.
Maybe that's why they are so unnecessarily complex.
If no-one can see how it works, no-one can correct it.
It's not a matter of seeing how it works, so much as finding the right point of view on the way it works.
I could put together transformers that worked for a long time before I got to grips with the transformer equation, which gave me a
clearer insight into what was going on.
--
Bill Sloman, Sydney
On 9/04/2025 11:57 pm, Edward Rawde wrote:
"Bill Sloman" <[email protected]> wrote in message news:vt4se2$3qshb$[email protected]...
On 9/04/2025 1:56 am, Edward Rawde wrote:
"Bill Sloman" <[email protected]> wrote in message news:vt2bck$1gmbm$[email protected]...
On 7/04/2025 11:10 pm, Edward Rawde wrote:
"Bill Sloman" <[email protected]> wrote in message news:vsvspr$33gdd$[email protected]...
On 7/04/2025 3:25 am, Edward Rawde wrote:
"Bill Sloman" <[email protected]> wrote in message news:vsuacb$1d4ec$[email protected]...
On 7/04/2025 12:39 am, Edward Rawde wrote:
"Bill Sloman" <[email protected]> wrote in message news:vsu092$14oc7$[email protected]...
On 6/04/2025 2:12 am, JM wrote:
On Fri, 4 Apr 2025 23:55:11 -0400, "Edward Rawde"
<[email protected]d> wrote:
"JM" <[email protected]> wrote in message news:[email protected]...
On Fri, 4 Apr 2025 16:29:27 -0400, "Edward Rawde"
<[email protected]d> wrote:
"JM" <[email protected]> wrote in message news:[email protected]...
On Fri, 4 Apr 2025 14:25:29 -0400, "Edward Rawde" >>>>>>>>>>>>>>>> <[email protected]d> wrote:
"Bill Sloman" <[email protected]> wrote in message news:vsnufh$2ou7j$[email protected]...
On 4/04/2025 11:33 am, JM wrote:...
On Thu, 3 Apr 2025 19:25:33 -0400, "Edward Rawde" >>>>>>>>>>>>>>>>>>> <[email protected]d> wrote:
"JM" <[email protected]> wrote in message news:[email protected]...
On Sun, 30 Mar 2025 14:54:56 -0400, "Edward Rawde" >>>>>>>>>>>>>>>>>>>>> <[email protected]d> wrote:
Not long ago JM posted a 1KHz sinewave oscillator with very low distortion.
It used a 470uF non polarized capacitor which in practice would probably be made from two 1000uF capacitors.
There's nothing wrong with that but I wanted to see whether I could make a working circuit without needing
such
a
large
capacitor.
You will need to adjust the feedback to suit. Start with a -5 or -6
gain block after the integrator and adjust it's gain until the startup
is clean (no saturation).
Here's my version of John May's variation. >>>>>>>>>>>>>>>>>>
Yes, that works but only 120dB down at 4KHz. >>>>>>>>>>>>>>>>> I put the damping resistor back to 47k since I don't care what happens during the first few seonds as long as it
happens.
If it's necessary to wait one minute for the purest tone, that's fine with me.
Linewraps are going to be a problem - delete all "\n" from the last few lines
You don't want to remove \n just remove the wraps. >>>>>>>>>>>>>>>>>
BCM61B does not have two independent transistors. >>>>>>>>>>>>>>>>>
So you probably want BCM847BS which has two independent matched transistors and a very low price at digikey, so
may
as
well
use
two
of them as shown below.
I took the model from
https://github.com/peteut/spice-models/blob/master/nxp/complex_discretes/complex_discretes.txt
It should only be necessary to unwrap the last line of the following.
Don't remove \n just remove the wraps, you may need to use a horizontal scroll bar.
Version 4.1
Best to just offset the integrator output so the amplitude is brought
under control sooner.
Wow. That has much lower distortion too.
If you just replace Q1,2 duals with a simple long tailed pair I think
you will get better performance.
I'm not sure I understand how the multiplier could be implemented with just a long tailed pair.
Just modulate the tail current and select how much to steer to the >>>>>>>>>>>> output by directly driving the bases rather than indirectly as in your
circuit. The following link shows one example topology, and a four
quadrant differential I/O version. Compare the linearity of each of
them.
https://1drv.ms/u/c/1af24d72a509cd48/EWVCUG7-jFJMu7-01VczCRcBzEC9JPHrV45x7TOunN90Gg?e=GXbvX5
It could be used as shown here.
https://1drv.ms/u/c/1af24d72a509cd48/EVmMVrvUD15GutoR5nCJ7QEBSeZsHWpHudqR0b8XtTLMLw?e=HIV74I
As I've already said, I like it. I've played with it a bit. >>>>>>>>>>>
The ON-Semiconductor NSS40301MDR2G NPN dual comes with a 2mV guaranteed maximum difference in base-emitter voltages (at
the
same
emitter current). Edward Rawde's Nexperia BCM61B dual part has matched current gain, but no guarantee on the Vbe. The
Nexperia
BCM847BS does offer 2mV base-emitter matching, and would presumably work just as well.
Putting in the ON-Semiconductor dual means that your gain control circuit doesn't have to waste output swing coping with
part-to-part variation.
I've added a cascode transistor (Q1, it should be Q4) to minimise any Early effect distortion.
I've snipped out the op amp driving the base of Q3. Once you'd gone AC-coupled, it wasn't doing anything useful.
And I've put a string of eight diodes in series with R10. They nominally compensate for the temperature dependence
introduced
by
the four rectifier diodes D2, D12, D13 and D14. In this version of the circuit the rectifiers knock about 0.6 volts off
a
sine
wave that peaks at 3.8V, about a quarter of the 15V rail. I haven't run the numbers to fix the best number of diodes,
but
something between six and eight looks okay.
The harmonics aren't great - most of them are about 90dB below the fundamental, but the seventh is only 85dB down.
Not sure I see the point if it's only 80dB down Bill.
@ 7Khz in LTSPice 24.1.5
LTSpice isn't all that reliable as predictor of low level distortion. Having an armoury of different circuits to try when
you
finally get around to building and testing something real may be useful.
I can almost get that from a simple phase shift oscillator and a 1KHz tuned circuit.
I'm sure that you think so. John Larkin thought that a bang-bang amplitude control was worth suggesting...
The last time I included a diode string like that in one of my circuits (which I seem to recall had better than 80dB
performance)
you told me it was nuts.
It probably was. In this case there are better ways of getting a rectified output than a simple series diode - I've posted
circuits which incorporate precision rectifiers which get rid of the forward drop through the diode, and I've built
circuits
that
used synchronous rectifiers built around transmission gates where the output isn't shifted by a temperature dependent
diode
drop.
It went into a GaAs single crystal puller as a retrofit.
The main point of the diode string was as a satirical comment on that aspect of the design you posted, which probably
counts
as
being hostile, but I am hostile to ill-thought out designs, hard though it is to get the design time to sort them out.
I don't see anything particularly hostile there Bill. Just different points of view.
I've got stuck with sorting out other peoples half-baked designs often enough, but only after my bosses had had their
noses
rubbed
in the unfortunate consequences.
When I started work as a fresh graduate (but one who also had practical experience with everything from TV antenna systems
in
hospitals to AY-3-8500 based games) I was amazed at some of the analogue circuit design blunders I encountered.
In one case I built a piece of custom test equipment which needed +15V and -15V. An available transformer had two suitable
isolated
secondary windings so I just used two 7815 devices.
Only to be told by a more experienced "Designer" that connecting the output of a 7815 to ground would short it out and I
had
to
use
7915 for that.....
What he should have said was the you were messing up the ground returns by hooking up the +15V output of the second 7815 to
the
0V
rail.
He was avoiding spending a long time talking about grounding and shielding, which is a rather specialised subject.
I see. Thank you for letting me know what he was thinking Bill.
Do you have some kind of time machine that you travel around in so you can have a better knowledge of what happened in a past
situation when compared with someone who was actually there at the time? >>>>>>
In this particular thread your eight transistor is bonkers, but it >>>>>>> works - not that I can see how.
Seems pretty obvious to me how it works Bill.
But John May could take out half the transistors and produce a circuit that still worked.
One reason for that is that a current source/sink can be approximated by a high value resistor so instead of using a current
mirror
a single resistor is likely to work fine.
You might need to reverse the polarity of the voltage drive but there are many ways to do that in this circuit.
And you haven't made any attempt to explain how it does work.
As I pointed out some time ago, you never explain how your circuits work Bill.
It's like you just expect others to accept that you have superior knowledge.
If you really could see what other people think then I think you might be surprised at the amount of laughter going on.
You can suspect what you like but that's just another example of you twisting the world into something you would like it to be.
If I didn't know how it was intended to work then it almost certainly would not work.
And suspect that that there were a lot of variations that didn't work >>>>
Anyone with any understanding of this circuit at all knows that a very basic explanation of how it works is that you need to
multiply the gain control level by a sample of the oscillator signal and feed the result back into the oscillator.
So if your signals are in the form of two currents which never change polarity then a one quadrant current multiplier should
work
fine.
You might then do some research to see if you can find any examples of circuits which meet that requirement.
https://www.google.com/search?q=one+quadrant+analog+current+multiplier&udm=2
Much like you might refer to Horowitz/Hill to see if there are any relevant example circuits.
I'm surprised that you can't see how it works.
I've got a rough idea, but not good enough to let me do anything interesting, or to write any kind of useful explanation of
what
is going on. Writing that kind of explanation is usually a necessary part of getting a circuit into production.
I've yet to see you write an explanation of how a circuit works Bill.
Instead I've only seen circuits using three or four times as many components as the last one JM posted in this thread and never
any
better than 70dB.
Then you get upset when the rest of the world tries to tell you that although your circuit may have a few good ideas in it,
it's
worthless from a meeting the requirements point of view.
Management needs it before they will spend the extra money on document the design for production, and the final test
technicians
and service engineers need it make sure that the circuit works and to be able to fix it when it doesn't.
John May could see how it worked, and how it could be simplified to four transistors - and eventually down
to two matched pairs.
You seem to be very good at knowing what other people can/could see Bill.
It's a necessary engineering skill. See above.
I prefer not to make any assumptions about what other people can or can't see.
Particularly when I know nothing at all about them other than what has been posted here.
Which you haven't measured on a real circuit yet. Since you don't seem to be all that sensitive to the risks from power supplyHe doesn't like it, and prefers the single
long-tailed pair approach, despite the fact that LTSpice says it >>>>>>> offers poorer performance.
He provided three examples. All of which obviously work.
The best one from my point of view is the one with lowest distortion. >>>>>
feedthrough, doing that might be painfully educational
Of course Bill. I have absolutely no doubt that you would take great delight in my pain.
And I have no doubt that you would not offer any meaningful assistance with the power supply design because you would rather
watch
me suffer.
Offering assistance could reduce my suffering which wouldn't do at all. >>>>
I'd probably use 6V batteries arranged for +/- 18V for a first test of a circuit like this.
With some series components for filtering and to stay below LT1679 36V max.
After all the goal, when I started looking into sinewave oscillators, was to see whether it's really necessary to use
thermistors,
lamps, opto devices or FETs.
Have you come to a conclusion yet? As I seem to have mentioned before, it strikes me that the answer is that it's obvious
necessary.
What's obviously necessary Bill?
The last circuit JM posted has no measurable distortion worth mentioning that I can see.
I like the long-tailed pair approach myself - I can see exactly how it works - but it's probably worth my time to work out
exactly how the four transistor circuit actually works, and why it seems to offer lower distortion in LTSpice simulations.
and the chance that I'd learn anything interesting is remote.It's not the kind of project that anybody would fund,
Ah well I'm sorry if you aren't likely to learn anything interesting Bill.
That's text-chopping.
I've learned a lot and will continue to do so.
We can hope.
I'd translate that into "I hope you never learn anything so I can continue to tell you how stupid you are".
That is a remarkably hostile reaction. Most engineers can eventually learn stuff, but some are slower at it than others.
Encouraging the slower ones takes quite a lot of effort because you have to go into quite a lot of detail before you can get the
message across,
I've never seen you explain in any level of detail how your own circuits work Bill.
All explanations are designed to work for the audience they are aimed at. You don't insult the intelligence of people like Phil
Hobbs by going into unnecessary detail. Lesser mortals may well feel short-changed.
Sloman A.W., Buggs P., Molloy J., and Stewart D. "A microcontroller-based driver to stabilise the temperature of an optical stage
to 1mK in the range 4C to 38C, using a Peltier heat pump and a thermistor sensor" Measurement Science and Technology, 7 1653-64
(1996) contains quite a lot of explanation, but I took care not to patronise the prospective audience by telling them more than I
needed to.
--
Bill Sloman, Sydney
--
Bill Sloman, Sydney
"Bill Sloman" <[email protected]> wrote in message news:vt4se2$3qshb$[email protected]...
On 9/04/2025 1:56 am, Edward Rawde wrote:
"Bill Sloman" <[email protected]> wrote in message news:vt2bck$1gmbm$[email protected]...
On 7/04/2025 11:10 pm, Edward Rawde wrote:
"Bill Sloman" <[email protected]> wrote in message news:vsvspr$33gdd$[email protected]...
On 7/04/2025 3:25 am, Edward Rawde wrote:
"Bill Sloman" <[email protected]> wrote in message news:vsuacb$1d4ec$[email protected]...
On 7/04/2025 12:39 am, Edward Rawde wrote:
"Bill Sloman" <[email protected]> wrote in message news:vsu092$14oc7$[email protected]...
On 6/04/2025 2:12 am, JM wrote:
On Fri, 4 Apr 2025 23:55:11 -0400, "Edward Rawde"
<[email protected]d> wrote:
"JM" <[email protected]> wrote in message news:[email protected]...
On Fri, 4 Apr 2025 16:29:27 -0400, "Edward Rawde"
<[email protected]d> wrote:
"JM" <[email protected]> wrote in message news:[email protected]...
On Fri, 4 Apr 2025 14:25:29 -0400, "Edward Rawde" >>>>>>>>>>>>>>> <[email protected]d> wrote:
"Bill Sloman" <[email protected]> wrote in message news:vsnufh$2ou7j$[email protected]...
On 4/04/2025 11:33 am, JM wrote:...
On Thu, 3 Apr 2025 19:25:33 -0400, "Edward Rawde" >>>>>>>>>>>>>>>>>> <[email protected]d> wrote:
"JM" <[email protected]> wrote in message news:[email protected]...
On Sun, 30 Mar 2025 14:54:56 -0400, "Edward Rawde" >>>>>>>>>>>>>>>>>>>> <[email protected]d> wrote:
Not long ago JM posted a 1KHz sinewave oscillator with very low distortion.
It used a 470uF non polarized capacitor which in practice would probably be made from two 1000uF capacitors.
There's nothing wrong with that but I wanted to see whether I could make a working circuit without needing such
a
large
capacitor.
You will need to adjust the feedback to suit. Start with a -5 or -6
gain block after the integrator and adjust it's gain until the startup
is clean (no saturation).
Here's my version of John May's variation.
Yes, that works but only 120dB down at 4KHz.
I put the damping resistor back to 47k since I don't care what happens during the first few seonds as long as it
happens.
If it's necessary to wait one minute for the purest tone, that's fine with me.
Linewraps are going to be a problem - delete all "\n" from the last few lines
You don't want to remove \n just remove the wraps. >>>>>>>>>>>>>>>>
BCM61B does not have two independent transistors. >>>>>>>>>>>>>>>>
So you probably want BCM847BS which has two independent matched transistors and a very low price at digikey, so may
as
well
use
two
of them as shown below.
I took the model from
https://github.com/peteut/spice-models/blob/master/nxp/complex_discretes/complex_discretes.txt
It should only be necessary to unwrap the last line of the following.
Don't remove \n just remove the wraps, you may need to use a horizontal scroll bar.
Version 4.1
Best to just offset the integrator output so the amplitude is brought
under control sooner.
Wow. That has much lower distortion too.
If you just replace Q1,2 duals with a simple long tailed pair I think
you will get better performance.
I'm not sure I understand how the multiplier could be implemented with just a long tailed pair.
Just modulate the tail current and select how much to steer to the >>>>>>>>>>> output by directly driving the bases rather than indirectly as in your
circuit. The following link shows one example topology, and a four >>>>>>>>>>> quadrant differential I/O version. Compare the linearity of each of
them.
https://1drv.ms/u/c/1af24d72a509cd48/EWVCUG7-jFJMu7-01VczCRcBzEC9JPHrV45x7TOunN90Gg?e=GXbvX5
It could be used as shown here.
https://1drv.ms/u/c/1af24d72a509cd48/EVmMVrvUD15GutoR5nCJ7QEBSeZsHWpHudqR0b8XtTLMLw?e=HIV74I
As I've already said, I like it. I've played with it a bit. >>>>>>>>>>
The ON-Semiconductor NSS40301MDR2G NPN dual comes with a 2mV guaranteed maximum difference in base-emitter voltages (at
the
same
emitter current). Edward Rawde's Nexperia BCM61B dual part has matched current gain, but no guarantee on the Vbe. The
Nexperia
BCM847BS does offer 2mV base-emitter matching, and would presumably work just as well.
Putting in the ON-Semiconductor dual means that your gain control circuit doesn't have to waste output swing coping with
part-to-part variation.
I've added a cascode transistor (Q1, it should be Q4) to minimise any Early effect distortion.
I've snipped out the op amp driving the base of Q3. Once you'd gone AC-coupled, it wasn't doing anything useful.
And I've put a string of eight diodes in series with R10. They nominally compensate for the temperature dependence
introduced
by
the four rectifier diodes D2, D12, D13 and D14. In this version of the circuit the rectifiers knock about 0.6 volts off a
sine
wave that peaks at 3.8V, about a quarter of the 15V rail. I haven't run the numbers to fix the best number of diodes, but
something between six and eight looks okay.
The harmonics aren't great - most of them are about 90dB below the fundamental, but the seventh is only 85dB down.
Not sure I see the point if it's only 80dB down Bill.
@ 7Khz in LTSPice 24.1.5
LTSpice isn't all that reliable as predictor of low level distortion. Having an armoury of different circuits to try when
you
finally get around to building and testing something real may be useful.
I can almost get that from a simple phase shift oscillator and a 1KHz tuned circuit.
I'm sure that you think so. John Larkin thought that a bang-bang amplitude control was worth suggesting...
The last time I included a diode string like that in one of my circuits (which I seem to recall had better than 80dB
performance)
you told me it was nuts.
It probably was. In this case there are better ways of getting a rectified output than a simple series diode - I've posted
circuits which incorporate precision rectifiers which get rid of the forward drop through the diode, and I've built circuits
that
used synchronous rectifiers built around transmission gates where the output isn't shifted by a temperature dependent diode
drop.
It went into a GaAs single crystal puller as a retrofit.
The main point of the diode string was as a satirical comment on that aspect of the design you posted, which probably counts
as
being hostile, but I am hostile to ill-thought out designs, hard though it is to get the design time to sort them out.
I don't see anything particularly hostile there Bill. Just different points of view.
I've got stuck with sorting out other peoples half-baked designs often enough, but only after my bosses had had their noses
rubbed
in the unfortunate consequences.
When I started work as a fresh graduate (but one who also had practical experience with everything from TV antenna systems in
hospitals to AY-3-8500 based games) I was amazed at some of the analogue circuit design blunders I encountered.
In one case I built a piece of custom test equipment which needed +15V and -15V. An available transformer had two suitable
isolated
secondary windings so I just used two 7815 devices.
Only to be told by a more experienced "Designer" that connecting the output of a 7815 to ground would short it out and I had
to
use
7915 for that.....
What he should have said was the you were messing up the ground returns by hooking up the +15V output of the second 7815 to
the
0V
rail.
He was avoiding spending a long time talking about grounding and shielding, which is a rather specialised subject.
I see. Thank you for letting me know what he was thinking Bill.
Do you have some kind of time machine that you travel around in so you can have a better knowledge of what happened in a past
situation when compared with someone who was actually there at the time? >>>>>
In this particular thread your eight transistor is bonkers, but it >>>>>> works - not that I can see how.
Seems pretty obvious to me how it works Bill.
But John May could take out half the transistors and produce a circuit that still worked.
One reason for that is that a current source/sink can be approximated by a high value resistor so instead of using a current
mirror
a single resistor is likely to work fine.
You might need to reverse the polarity of the voltage drive but there are many ways to do that in this circuit.
And you haven't made any attempt to explain how it does work.
As I pointed out some time ago, you never explain how your circuits work Bill.
It's like you just expect others to accept that you have superior knowledge.
If you really could see what other people think then I think you might be surprised at the amount of laughter going on.
If I didn't know how it was intended to work then it almost certainly would not work.
And suspect that that there were a lot of variations that didn't work
You can suspect what you like but that's just another example of you twisting the world into something you would like it to be.
Anyone with any understanding of this circuit at all knows that a very basic explanation of how it works is that you need to
multiply the gain control level by a sample of the oscillator signal and feed the result back into the oscillator.
So if your signals are in the form of two currents which never change polarity then a one quadrant current multiplier should work
fine.
You might then do some research to see if you can find any examples of circuits which meet that requirement.
https://www.google.com/search?q=one+quadrant+analog+current+multiplier&udm=2
Much like you might refer to Horowitz/Hill to see if there are any relevant example circuits.
I'm surprised that you can't see how it works.
I've got a rough idea, but not good enough to let me do anything interesting, or to write any kind of useful explanation of what
is going on. Writing that kind of explanation is usually a necessary part of getting a circuit into production.
I've yet to see you write an explanation of how a circuit works Bill.
Instead I've only seen circuits using three or four times as many components as the last one JM posted in this thread and never
any
better than 70dB.
Then you get upset when the rest of the world tries to tell you that although your circuit may have a few good ideas in it, it's
worthless from a meeting the requirements point of view.
Management needs it before they will spend the extra money on document the design for production, and the final test technicians
and service engineers need it make sure that the circuit works and to be able to fix it when it doesn't.
It's a necessary engineering skill. See above.John May could see how it worked, and how it could be simplified to four transistors - and eventually down
to two matched pairs.
You seem to be very good at knowing what other people can/could see Bill. >>>>
I prefer not to make any assumptions about what other people can or can't see.
Particularly when I know nothing at all about them other than what has been posted here.
Which you haven't measured on a real circuit yet. Since you don't seem to be all that sensitive to the risks from power supplyHe doesn't like it, and prefers the single
long-tailed pair approach, despite the fact that LTSpice says it
offers poorer performance.
He provided three examples. All of which obviously work.
The best one from my point of view is the one with lowest distortion. >>>>
feedthrough, doing that might be painfully educational
Of course Bill. I have absolutely no doubt that you would take great delight in my pain.
And I have no doubt that you would not offer any meaningful assistance with the power supply design because you would rather
watch
me suffer.
Offering assistance could reduce my suffering which wouldn't do at all.
I'd probably use 6V batteries arranged for +/- 18V for a first test of a circuit like this.
With some series components for filtering and to stay below LT1679 36V max. >>>
After all the goal, when I started looking into sinewave oscillators, was to see whether it's really necessary to use
thermistors,
lamps, opto devices or FETs.
Have you come to a conclusion yet? As I seem to have mentioned before, it strikes me that the answer is that it's obvious
necessary.
What's obviously necessary Bill?
The last circuit JM posted has no measurable distortion worth mentioning that I can see.
I like the long-tailed pair approach myself - I can see exactly how it works - but it's probably worth my time to work out
exactly how the four transistor circuit actually works, and why it seems to offer lower distortion in LTSpice simulations. >>>>>> It's not the kind of project that anybody would fund,
and the chance that I'd learn anything interesting is remote.
Ah well I'm sorry if you aren't likely to learn anything interesting Bill.
That's text-chopping.
I've learned a lot and will continue to do so.
We can hope.
I'd translate that into "I hope you never learn anything so I can continue to tell you how stupid you are".
That is a remarkably hostile reaction. Most engineers can eventually learn stuff, but some are slower at it than others.
Encouraging the slower ones takes quite a lot of effort because you have to go into quite a lot of detail before you can get the
message across,
I've never seen you explain in any level of detail how your own circuits work Bill.
"Bill Sloman" <[email protected]> wrote in message news:vt60p8$q8qf$[email protected]...
On 9/04/2025 11:57 pm, Edward Rawde wrote:
"Bill Sloman" <[email protected]> wrote in message news:vt4se2$3qshb$[email protected]...
On 9/04/2025 1:56 am, Edward Rawde wrote:
"Bill Sloman" <[email protected]> wrote in message news:vt2bck$1gmbm$[email protected]...
On 7/04/2025 11:10 pm, Edward Rawde wrote:
"Bill Sloman" <[email protected]> wrote in message news:vsvspr$33gdd$[email protected]...
On 7/04/2025 3:25 am, Edward Rawde wrote:
"Bill Sloman" <[email protected]> wrote in message news:vsuacb$1d4ec$[email protected]...
On 7/04/2025 12:39 am, Edward Rawde wrote:
"Bill Sloman" <[email protected]> wrote in message news:vsu092$14oc7$[email protected]...
On 6/04/2025 2:12 am, JM wrote:
On Fri, 4 Apr 2025 23:55:11 -0400, "Edward Rawde"
<[email protected]d> wrote:
"JM" <[email protected]> wrote in message news:[email protected]...
On Fri, 4 Apr 2025 16:29:27 -0400, "Edward Rawde" >>>>>>>>>>>>>>> <[email protected]d> wrote:
"JM" <[email protected]> wrote in message news:[email protected]...
On Fri, 4 Apr 2025 14:25:29 -0400, "Edward Rawde" >>>>>>>>>>>>>>>>> <[email protected]d> wrote:
"Bill Sloman" <[email protected]> wrote in message news:vsnufh$2ou7j$[email protected]...
On 4/04/2025 11:33 am, JM wrote:...
On Thu, 3 Apr 2025 19:25:33 -0400, "Edward Rawde" >>>>>>>>>>>>>>>>>>>> <[email protected]d> wrote:
"JM" <[email protected]> wrote in message news:[email protected]...
On Sun, 30 Mar 2025 14:54:56 -0400, "Edward Rawde" >>>>>>>>>>>>>>>>>>>>>> <[email protected]d> wrote:
Not long ago JM posted a 1KHz sinewave oscillator with very low distortion.
It used a 470uF non polarized capacitor which in practice would probably be made from two 1000uF capacitors.
There's nothing wrong with that but I wanted to see whether I could make a working circuit without needing
such
a
large
capacitor.
You will need to adjust the feedback to suit. Start with a -5 or -6
gain block after the integrator and adjust it's gain until the startup
is clean (no saturation).
Here's my version of John May's variation. >>>>>>>>>>>>>>>>>>>
Yes, that works but only 120dB down at 4KHz. >>>>>>>>>>>>>>>>>> I put the damping resistor back to 47k since I don't care what happens during the first few seonds as long as it
happens.
If it's necessary to wait one minute for the purest tone, that's fine with me.
Linewraps are going to be a problem - delete all "\n" from the last few lines
You don't want to remove \n just remove the wraps. >>>>>>>>>>>>>>>>>>
BCM61B does not have two independent transistors. >>>>>>>>>>>>>>>>>>
So you probably want BCM847BS which has two independent matched transistors and a very low price at digikey, so
may
as
well
use
two
of them as shown below.
I took the model from
https://github.com/peteut/spice-models/blob/master/nxp/complex_discretes/complex_discretes.txt
It should only be necessary to unwrap the last line of the following.
Don't remove \n just remove the wraps, you may need to use a horizontal scroll bar.
Version 4.1
Best to just offset the integrator output so the amplitude is brought
under control sooner.
Wow. That has much lower distortion too.
If you just replace Q1,2 duals with a simple long tailed pair I think
you will get better performance.
I'm not sure I understand how the multiplier could be implemented with just a long tailed pair.
Just modulate the tail current and select how much to steer to the
output by directly driving the bases rather than indirectly as in your
circuit. The following link shows one example topology, and a four
quadrant differential I/O version. Compare the linearity of each of
them.
https://1drv.ms/u/c/1af24d72a509cd48/EWVCUG7-jFJMu7-01VczCRcBzEC9JPHrV45x7TOunN90Gg?e=GXbvX5
It could be used as shown here.
https://1drv.ms/u/c/1af24d72a509cd48/EVmMVrvUD15GutoR5nCJ7QEBSeZsHWpHudqR0b8XtTLMLw?e=HIV74I
As I've already said, I like it. I've played with it a bit. >>>>>>>>>>>>
The ON-Semiconductor NSS40301MDR2G NPN dual comes with a 2mV guaranteed maximum difference in base-emitter voltages (at
the
same
emitter current). Edward Rawde's Nexperia BCM61B dual part has matched current gain, but no guarantee on the Vbe. The
Nexperia
BCM847BS does offer 2mV base-emitter matching, and would presumably work just as well.
Putting in the ON-Semiconductor dual means that your gain control circuit doesn't have to waste output swing coping with
part-to-part variation.
I've added a cascode transistor (Q1, it should be Q4) to minimise any Early effect distortion.
I've snipped out the op amp driving the base of Q3. Once you'd gone AC-coupled, it wasn't doing anything useful.
And I've put a string of eight diodes in series with R10. They nominally compensate for the temperature dependence
introduced
by
the four rectifier diodes D2, D12, D13 and D14. In this version of the circuit the rectifiers knock about 0.6 volts off
a
sine
wave that peaks at 3.8V, about a quarter of the 15V rail. I haven't run the numbers to fix the best number of diodes,
but
something between six and eight looks okay.
The harmonics aren't great - most of them are about 90dB below the fundamental, but the seventh is only 85dB down.
Not sure I see the point if it's only 80dB down Bill.
@ 7Khz in LTSPice 24.1.5
LTSpice isn't all that reliable as predictor of low level distortion. Having an armoury of different circuits to try when
you
finally get around to building and testing something real may be useful.
I can almost get that from a simple phase shift oscillator and a 1KHz tuned circuit.
I'm sure that you think so. John Larkin thought that a bang-bang amplitude control was worth suggesting...
The last time I included a diode string like that in one of my circuits (which I seem to recall had better than 80dB
performance)
you told me it was nuts.
It probably was. In this case there are better ways of getting a rectified output than a simple series diode - I've posted
circuits which incorporate precision rectifiers which get rid of the forward drop through the diode, and I've built
circuits
that
used synchronous rectifiers built around transmission gates where the output isn't shifted by a temperature dependent
diode
drop.
It went into a GaAs single crystal puller as a retrofit.
The main point of the diode string was as a satirical comment on that aspect of the design you posted, which probably
counts
as
being hostile, but I am hostile to ill-thought out designs, hard though it is to get the design time to sort them out.
I don't see anything particularly hostile there Bill. Just different points of view.
I've got stuck with sorting out other peoples half-baked designs often enough, but only after my bosses had had their
noses
rubbed
in the unfortunate consequences.
When I started work as a fresh graduate (but one who also had practical experience with everything from TV antenna systems
in
hospitals to AY-3-8500 based games) I was amazed at some of the analogue circuit design blunders I encountered.
In one case I built a piece of custom test equipment which needed +15V and -15V. An available transformer had two suitable
isolated
secondary windings so I just used two 7815 devices.
Only to be told by a more experienced "Designer" that connecting the output of a 7815 to ground would short it out and I
had
to
use
7915 for that.....
What he should have said was the you were messing up the ground returns by hooking up the +15V output of the second 7815 to
the
0V
rail.
He was avoiding spending a long time talking about grounding and shielding, which is a rather specialised subject.
I see. Thank you for letting me know what he was thinking Bill.
Do you have some kind of time machine that you travel around in so you can have a better knowledge of what happened in a past
situation when compared with someone who was actually there at the time?
In this particular thread your eight transistor is bonkers, but it >>>>>>>> works - not that I can see how.
Seems pretty obvious to me how it works Bill.
But John May could take out half the transistors and produce a circuit that still worked.
One reason for that is that a current source/sink can be approximated by a high value resistor so instead of using a current
mirror
a single resistor is likely to work fine.
You might need to reverse the polarity of the voltage drive but there are many ways to do that in this circuit.
And you haven't made any attempt to explain how it does work.
As I pointed out some time ago, you never explain how your circuits work Bill.
It's like you just expect others to accept that you have superior knowledge.
If you really could see what other people think then I think you might be surprised at the amount of laughter going on.
You can suspect what you like but that's just another example of you twisting the world into something you would like it to be.
If I didn't know how it was intended to work then it almost certainly would not work.
And suspect that that there were a lot of variations that didn't work >>>>>
Anyone with any understanding of this circuit at all knows that a very basic explanation of how it works is that you need to
multiply the gain control level by a sample of the oscillator signal and feed the result back into the oscillator.
So if your signals are in the form of two currents which never change polarity then a one quadrant current multiplier should
work
fine.
You might then do some research to see if you can find any examples of circuits which meet that requirement.
https://www.google.com/search?q=one+quadrant+analog+current+multiplier&udm=2
Much like you might refer to Horowitz/Hill to see if there are any relevant example circuits.
I'm surprised that you can't see how it works.
I've got a rough idea, but not good enough to let me do anything interesting, or to write any kind of useful explanation of
what
is going on. Writing that kind of explanation is usually a necessary part of getting a circuit into production.
I've yet to see you write an explanation of how a circuit works Bill. >>>>> Instead I've only seen circuits using three or four times as many components as the last one JM posted in this thread and never
any
better than 70dB.
Then you get upset when the rest of the world tries to tell you that although your circuit may have a few good ideas in it,
it's
worthless from a meeting the requirements point of view.
Management needs it before they will spend the extra money on document the design for production, and the final test
technicians
and service engineers need it make sure that the circuit works and to be able to fix it when it doesn't.
John May could see how it worked, and how it could be simplified to four transistors - and eventually down
to two matched pairs.
You seem to be very good at knowing what other people can/could see Bill.
It's a necessary engineering skill. See above.
I prefer not to make any assumptions about what other people can or can't see.
Particularly when I know nothing at all about them other than what has been posted here.
Which you haven't measured on a real circuit yet. Since you don't seem to be all that sensitive to the risks from power supplyHe doesn't like it, and prefers the single
long-tailed pair approach, despite the fact that LTSpice says it >>>>>>>> offers poorer performance.
He provided three examples. All of which obviously work.
The best one from my point of view is the one with lowest distortion. >>>>>>
feedthrough, doing that might be painfully educational
Of course Bill. I have absolutely no doubt that you would take great delight in my pain.
And I have no doubt that you would not offer any meaningful assistance with the power supply design because you would rather
watch
me suffer.
Offering assistance could reduce my suffering which wouldn't do at all. >>>>>
I'd probably use 6V batteries arranged for +/- 18V for a first test of a circuit like this.
With some series components for filtering and to stay below LT1679 36V max.
After all the goal, when I started looking into sinewave oscillators, was to see whether it's really necessary to use
thermistors,
lamps, opto devices or FETs.
Have you come to a conclusion yet? As I seem to have mentioned before, it strikes me that the answer is that it's obvious
necessary.
What's obviously necessary Bill?
The last circuit JM posted has no measurable distortion worth mentioning that I can see.
I like the long-tailed pair approach myself - I can see exactly how it works - but it's probably worth my time to work out
exactly how the four transistor circuit actually works, and why it seems to offer lower distortion in LTSpice simulations.
>>>>>> It's not the kind of project that anybody would fund, >>>>>>>> and the chance that I'd learn anything interesting is remote.
Ah well I'm sorry if you aren't likely to learn anything interesting Bill.
That's text-chopping.
I've learned a lot and will continue to do so.
We can hope.
I'd translate that into "I hope you never learn anything so I can continue to tell you how stupid you are".
That is a remarkably hostile reaction. Most engineers can eventually learn stuff, but some are slower at it than others.
Encouraging the slower ones takes quite a lot of effort because you have to go into quite a lot of detail before you can get the
message across,
I've never seen you explain in any level of detail how your own circuits work Bill.
All explanations are designed to work for the audience they are aimed at. You don't insult the intelligence of people like Phil
Hobbs by going into unnecessary detail. Lesser mortals may well feel short-changed.
I don't speak for Phil Hobbs or anyone else but I think Phil would be impressed with a well thought out highly detailed explanation
of how a circuit works.
He would not be at all insulted no matter what the level of detail was.
Sloman A.W., Buggs P., Molloy J., and Stewart D. "A microcontroller-based driver to stabilise the temperature of an optical stage
to 1mK in the range 4C to 38C, using a Peltier heat pump and a thermistor sensor" Measurement Science and Technology, 7 1653-64
(1996) contains quite a lot of explanation, but I took care not to patronise the prospective audience by telling them more than I
needed to.
On 10/04/2025 1:14 am, Edward Rawde wrote:
"Bill Sloman" <[email protected]> wrote in message news:vt60p8$q8qf$[email protected]...
On 9/04/2025 11:57 pm, Edward Rawde wrote:
"Bill Sloman" <[email protected]> wrote in message news:vt4se2$3qshb$[email protected]...
On 9/04/2025 1:56 am, Edward Rawde wrote:
"Bill Sloman" <[email protected]> wrote in message news:vt2bck$1gmbm$[email protected]...
On 7/04/2025 11:10 pm, Edward Rawde wrote:
"Bill Sloman" <[email protected]> wrote in message news:vsvspr$33gdd$[email protected]...
On 7/04/2025 3:25 am, Edward Rawde wrote:
"Bill Sloman" <[email protected]> wrote in message news:vsuacb$1d4ec$[email protected]...
On 7/04/2025 12:39 am, Edward Rawde wrote:
"Bill Sloman" <[email protected]> wrote in message news:vsu092$14oc7$[email protected]...
On 6/04/2025 2:12 am, JM wrote:
On Fri, 4 Apr 2025 23:55:11 -0400, "Edward Rawde"
<[email protected]d> wrote:
"JM" <[email protected]> wrote in message news:[email protected]...
On Fri, 4 Apr 2025 16:29:27 -0400, "Edward Rawde" >>>>>>>>>>>>>>>> <[email protected]d> wrote:
"JM" <[email protected]> wrote in message news:[email protected]...
On Fri, 4 Apr 2025 14:25:29 -0400, "Edward Rawde" >>>>>>>>>>>>>>>>>> <[email protected]d> wrote:
"Bill Sloman" <[email protected]> wrote in message news:vsnufh$2ou7j$[email protected]...
On 4/04/2025 11:33 am, JM wrote:...
On Thu, 3 Apr 2025 19:25:33 -0400, "Edward Rawde" >>>>>>>>>>>>>>>>>>>>> <[email protected]d> wrote:
"JM" <[email protected]> wrote in message news:[email protected]...
On Sun, 30 Mar 2025 14:54:56 -0400, "Edward Rawde" >>>>>>>>>>>>>>>>>>>>>>> <[email protected]d> wrote: >>>>>>>>>>>>>>>>>>>>>>>
Not long ago JM posted a 1KHz sinewave oscillator with very low distortion.
It used a 470uF non polarized capacitor which in practice would probably be made from two 1000uF
capacitors.
There's nothing wrong with that but I wanted to see whether I could make a working circuit without needing
such
a
large
capacitor.
You will need to adjust the feedback to suit. Start with a -5 or -6
gain block after the integrator and adjust it's gain until the startup
is clean (no saturation).
Here's my version of John May's variation. >>>>>>>>>>>>>>>>>>>>
Yes, that works but only 120dB down at 4KHz. >>>>>>>>>>>>>>>>>>> I put the damping resistor back to 47k since I don't care what happens during the first few seonds as long as it
happens.
If it's necessary to wait one minute for the purest tone, that's fine with me.
Linewraps are going to be a problem - delete all "\n" from the last few lines
You don't want to remove \n just remove the wraps. >>>>>>>>>>>>>>>>>>>
BCM61B does not have two independent transistors. >>>>>>>>>>>>>>>>>>>
So you probably want BCM847BS which has two independent matched transistors and a very low price at digikey, so
may
as
well
use
two
of them as shown below.
I took the model from
https://github.com/peteut/spice-models/blob/master/nxp/complex_discretes/complex_discretes.txt
It should only be necessary to unwrap the last line of the following.
Don't remove \n just remove the wraps, you may need to use a horizontal scroll bar.
Version 4.1
Best to just offset the integrator output so the amplitude is brought
under control sooner.
Wow. That has much lower distortion too.
If you just replace Q1,2 duals with a simple long tailed pair I think
you will get better performance.
I'm not sure I understand how the multiplier could be implemented with just a long tailed pair.
Just modulate the tail current and select how much to steer to the
output by directly driving the bases rather than indirectly as in your
circuit. The following link shows one example topology, and a four
quadrant differential I/O version. Compare the linearity of each of
them.
https://1drv.ms/u/c/1af24d72a509cd48/EWVCUG7-jFJMu7-01VczCRcBzEC9JPHrV45x7TOunN90Gg?e=GXbvX5
It could be used as shown here.
https://1drv.ms/u/c/1af24d72a509cd48/EVmMVrvUD15GutoR5nCJ7QEBSeZsHWpHudqR0b8XtTLMLw?e=HIV74I
As I've already said, I like it. I've played with it a bit. >>>>>>>>>>>>>
The ON-Semiconductor NSS40301MDR2G NPN dual comes with a 2mV guaranteed maximum difference in base-emitter voltages
(at
the
same
emitter current). Edward Rawde's Nexperia BCM61B dual part has matched current gain, but no guarantee on the Vbe. The
Nexperia
BCM847BS does offer 2mV base-emitter matching, and would presumably work just as well.
Putting in the ON-Semiconductor dual means that your gain control circuit doesn't have to waste output swing coping
with
part-to-part variation.
I've added a cascode transistor (Q1, it should be Q4) to minimise any Early effect distortion.
I've snipped out the op amp driving the base of Q3. Once you'd gone AC-coupled, it wasn't doing anything useful.
And I've put a string of eight diodes in series with R10. They nominally compensate for the temperature dependence
introduced
by
the four rectifier diodes D2, D12, D13 and D14. In this version of the circuit the rectifiers knock about 0.6 volts
off
a
sine
wave that peaks at 3.8V, about a quarter of the 15V rail. I haven't run the numbers to fix the best number of diodes,
but
something between six and eight looks okay.
The harmonics aren't great - most of them are about 90dB below the fundamental, but the seventh is only 85dB down.
Not sure I see the point if it's only 80dB down Bill.
@ 7Khz in LTSPice 24.1.5
LTSpice isn't all that reliable as predictor of low level distortion. Having an armoury of different circuits to try
when
you
finally get around to building and testing something real may be useful.
I can almost get that from a simple phase shift oscillator and a 1KHz tuned circuit.
I'm sure that you think so. John Larkin thought that a bang-bang amplitude control was worth suggesting...
The last time I included a diode string like that in one of my circuits (which I seem to recall had better than 80dB
performance)
you told me it was nuts.
It probably was. In this case there are better ways of getting a rectified output than a simple series diode - I've
posted
circuits which incorporate precision rectifiers which get rid of the forward drop through the diode, and I've built
circuits
that
used synchronous rectifiers built around transmission gates where the output isn't shifted by a temperature dependent
diode
drop.
It went into a GaAs single crystal puller as a retrofit. >>>>>>>>>>>
The main point of the diode string was as a satirical comment on that aspect of the design you posted, which probably
counts
as
being hostile, but I am hostile to ill-thought out designs, hard though it is to get the design time to sort them out.
I don't see anything particularly hostile there Bill. Just different points of view.
I've got stuck with sorting out other peoples half-baked designs often enough, but only after my bosses had had their
noses
rubbed
in the unfortunate consequences.
When I started work as a fresh graduate (but one who also had practical experience with everything from TV antenna
systems
in
hospitals to AY-3-8500 based games) I was amazed at some of the analogue circuit design blunders I encountered.
In one case I built a piece of custom test equipment which needed +15V and -15V. An available transformer had two
suitable
isolated
secondary windings so I just used two 7815 devices.
Only to be told by a more experienced "Designer" that connecting the output of a 7815 to ground would short it out and I
had
to
use
7915 for that.....
What he should have said was the you were messing up the ground returns by hooking up the +15V output of the second 7815
to
the
0V
rail.
He was avoiding spending a long time talking about grounding and shielding, which is a rather specialised subject.
I see. Thank you for letting me know what he was thinking Bill. >>>>>>>> Do you have some kind of time machine that you travel around in so you can have a better knowledge of what happened in a
past
situation when compared with someone who was actually there at the time?
In this particular thread your eight transistor is bonkers, but it >>>>>>>>> works - not that I can see how.
Seems pretty obvious to me how it works Bill.
But John May could take out half the transistors and produce a circuit that still worked.
One reason for that is that a current source/sink can be approximated by a high value resistor so instead of using a current
mirror
a single resistor is likely to work fine.
You might need to reverse the polarity of the voltage drive but there are many ways to do that in this circuit.
And you haven't made any attempt to explain how it does work.
As I pointed out some time ago, you never explain how your circuits work Bill.
It's like you just expect others to accept that you have superior knowledge.
If you really could see what other people think then I think you might be surprised at the amount of laughter going on.
You can suspect what you like but that's just another example of you twisting the world into something you would like it to
If I didn't know how it was intended to work then it almost certainly would not work.
And suspect that that there were a lot of variations that didn't work >>>>>>
be.
Anyone with any understanding of this circuit at all knows that a very basic explanation of how it works is that you need to
multiply the gain control level by a sample of the oscillator signal and feed the result back into the oscillator.
So if your signals are in the form of two currents which never change polarity then a one quadrant current multiplier should
work
fine.
You might then do some research to see if you can find any examples of circuits which meet that requirement.
https://www.google.com/search?q=one+quadrant+analog+current+multiplier&udm=2
Much like you might refer to Horowitz/Hill to see if there are any relevant example circuits.
I'm surprised that you can't see how it works.
I've got a rough idea, but not good enough to let me do anything interesting, or to write any kind of useful explanation of
what
is going on. Writing that kind of explanation is usually a necessary part of getting a circuit into production.
I've yet to see you write an explanation of how a circuit works Bill. >>>>>> Instead I've only seen circuits using three or four times as many components as the last one JM posted in this thread and
never
any
better than 70dB.
Then you get upset when the rest of the world tries to tell you that although your circuit may have a few good ideas in it,
it's
worthless from a meeting the requirements point of view.
Management needs it before they will spend the extra money on document the design for production, and the final test
technicians
and service engineers need it make sure that the circuit works and to be able to fix it when it doesn't.
John May could see how it worked, and how it could be simplified to four transistors - and eventually down
to two matched pairs.
You seem to be very good at knowing what other people can/could see Bill.
It's a necessary engineering skill. See above.
I prefer not to make any assumptions about what other people can or can't see.
Particularly when I know nothing at all about them other than what has been posted here.
Which you haven't measured on a real circuit yet. Since you don't seem to be all that sensitive to the risks from powerHe doesn't like it, and prefers the single
long-tailed pair approach, despite the fact that LTSpice says it >>>>>>>>> offers poorer performance.
He provided three examples. All of which obviously work.
The best one from my point of view is the one with lowest distortion. >>>>>>>
supply
feedthrough, doing that might be painfully educational
Of course Bill. I have absolutely no doubt that you would take great delight in my pain.
And I have no doubt that you would not offer any meaningful assistance with the power supply design because you would rather
watch
me suffer.
Offering assistance could reduce my suffering which wouldn't do at all. >>>>>>
I'd probably use 6V batteries arranged for +/- 18V for a first test of a circuit like this.
With some series components for filtering and to stay below LT1679 36V max.
After all the goal, when I started looking into sinewave oscillators, was to see whether it's really necessary to use
thermistors,
lamps, opto devices or FETs.
Have you come to a conclusion yet? As I seem to have mentioned before, it strikes me that the answer is that it's obvious
necessary.
What's obviously necessary Bill?
The last circuit JM posted has no measurable distortion worth mentioning that I can see.
I like the long-tailed pair approach myself - I can see exactly how it works - but it's probably worth my time to work outAh well I'm sorry if you aren't likely to learn anything interesting Bill.
exactly how the four transistor circuit actually works, and why it seems to offer lower distortion in LTSpice simulations.
>>>>>> It's not the kind of project that anybody would fund, >>>>>>>>> and the chance that I'd learn anything interesting is remote. >>>>>>>>
That's text-chopping.
I've learned a lot and will continue to do so.
We can hope.
I'd translate that into "I hope you never learn anything so I can continue to tell you how stupid you are".
That is a remarkably hostile reaction. Most engineers can eventually learn stuff, but some are slower at it than others.
Encouraging the slower ones takes quite a lot of effort because you have to go into quite a lot of detail before you can get
the
message across,
I've never seen you explain in any level of detail how your own circuits work Bill.
All explanations are designed to work for the audience they are aimed at. You don't insult the intelligence of people like Phil
Hobbs by going into unnecessary detail. Lesser mortals may well feel short-changed.
I don't speak for Phil Hobbs or anyone else but I think Phil would be impressed with a well thought out highly detailed
explanation
of how a circuit works.
In the appropriate context. Sci.electronics.design has tended to brevity over the twenty-odd years I've been posting here and
following the posts.
He would not be at all insulted no matter what the level of detail was.
The phrase "insult the intelligence" doesn't refer to be people feeling insulted - rather to them being bored by unnecessary
detail. He probably wouldn't feel insulted but he'd probably skip most of the detail.
The reference to explanations in different contexts doesn't seem to have registered with you.
Sloman A.W., Buggs P., Molloy J., and Stewart D. "A microcontroller-based driver to stabilise the temperature of an optical
stage
to 1mK in the range 4C to 38C, using a Peltier heat pump and a thermistor sensor" Measurement Science and Technology, 7 1653-64
(1996) contains quite a lot of explanation, but I took care not to patronise the prospective audience by telling them more than
I
needed to.
--
Bill Sloman, Sydney
On Tue, 8 Apr 2025 21:04:25 -0400, "Edward Rawde"
<[email protected]d> wrote:
"JM" <[email protected]> wrote in message news:[email protected]...
On Tue, 8 Apr 2025 14:41:44 -0400, "Edward Rawde"
<[email protected]d> wrote:
"JM" <[email protected]> wrote in message news:[email protected]...
On Mon, 7 Apr 2025 22:46:13 -0400, "Edward Rawde"Thanks. That has the lowest distortion I've seen in a simulation so far. >>>>
<[email protected]d> wrote:
"Edward Rawde" <[email protected]d> wrote in message news:vsso97$1imi$[email protected]...
"JM" <[email protected]> wrote in message news:[email protected]...
On Fri, 4 Apr 2025 23:55:11 -0400, "Edward Rawde"
<[email protected]d> wrote:
"JM" <[email protected]> wrote in message news:[email protected]...
On Fri, 4 Apr 2025 16:29:27 -0400, "Edward Rawde"
<[email protected]d> wrote:
"JM" <[email protected]> wrote in message news:[email protected]...
On Fri, 4 Apr 2025 14:25:29 -0400, "Edward Rawde"
<[email protected]d> wrote:
"Bill Sloman" <[email protected]> wrote in message news:vsnufh$2ou7j$[email protected]...
On 4/04/2025 11:33 am, JM wrote:
On Thu, 3 Apr 2025 19:25:33 -0400, "Edward Rawde" >>>>>>>>>>>>>>> <[email protected]d> wrote:....
"JM" <[email protected]> wrote in message news:[email protected]...
On Sun, 30 Mar 2025 14:54:56 -0400, "Edward Rawde" >>>>>>>>>>>>>>>>> <[email protected]d> wrote:
Not long ago JM posted a 1KHz sinewave oscillator with very low distortion.
It used a 470uF non polarized capacitor which in practice would probably be made from two 1000uF capacitors.
There's nothing wrong with that but I wanted to see whether I could make a working circuit without needing such a
large
capacitor.
Here's an almost fully practical circuit except for the current sources and sinks.
I reversed the polarity of the control feedback and applied it to the >>>>> inverting input of the first oscilllator stage, removed some
redundant capacitors, and added some filtering to the gain control
signal. Also altered some gain values to improve the dynamics (but
that still has to be addressed).
Most real world designs would use a sample and hold circuit to sample >>>>> the output at it's maximum point and use that to control the feedback, >>>>> similar to the topology I think I posted a while ago. It might be
worthwhile looking at that.
I can't find the sample/hold circuit you mentioned, would you mind reposting it?
Thank you for your help with this. It is much appreciated.
Is the sample/hold circuit the one below?
After much digging I found it in a very interesting thread started by Bill Sloman on 5th February 2025 "The low distortion
oscillator problem".
I can't get it to simulate in 24.1.5
something to do with unknown parameter in table{-2m,0,2m,1}
Yes. Change the braces to brackets. Example use shown below. H2,3
should be circa -170(ish)dBc. Note that I have switched most op amps
outwith the control loop to simple models so that you can investigate
the control loop in isolation (it's fairly easy to implement the
sampling in hardware and it will be close to this in performance).
Compare the circuit below with one with the original polyphase
sampling (leave in the simple models) to determine any benefit. You
are already beyond the point where real opamps will limit the
performance - in this particular oscillator design.
"Bill Sloman" <[email protected]> wrote in message news:vt60p8$q8qf$[email protected]...
On 9/04/2025 11:57 pm, Edward Rawde wrote:
"Bill Sloman" <[email protected]> wrote in message news:vt4se2$3qshb$[email protected]...
On 9/04/2025 1:56 am, Edward Rawde wrote:
"Bill Sloman" <[email protected]> wrote in message news:vt2bck$1gmbm$[email protected]...
On 7/04/2025 11:10 pm, Edward Rawde wrote:
"Bill Sloman" <[email protected]> wrote in message news:vsvspr$33gdd$[email protected]...
On 7/04/2025 3:25 am, Edward Rawde wrote:
"Bill Sloman" <[email protected]> wrote in message news:vsuacb$1d4ec$[email protected]...
On 7/04/2025 12:39 am, Edward Rawde wrote:
"Bill Sloman" <[email protected]> wrote in message news:vsu092$14oc7$[email protected]...
On 6/04/2025 2:12 am, JM wrote:
On Fri, 4 Apr 2025 23:55:11 -0400, "Edward Rawde"
<[email protected]d> wrote:
"JM" <[email protected]> wrote in message news:[email protected]...
On Fri, 4 Apr 2025 16:29:27 -0400, "Edward Rawde" >>>>>>>>>>>>>>> <[email protected]d> wrote:
"JM" <[email protected]> wrote in message news:[email protected]...
On Fri, 4 Apr 2025 14:25:29 -0400, "Edward Rawde" >>>>>>>>>>>>>>>>> <[email protected]d> wrote:
"Bill Sloman" <[email protected]> wrote in message news:vsnufh$2ou7j$[email protected]...
On 4/04/2025 11:33 am, JM wrote:...
On Thu, 3 Apr 2025 19:25:33 -0400, "Edward Rawde" >>>>>>>>>>>>>>>>>>>> <[email protected]d> wrote:
"JM" <[email protected]> wrote in message news:[email protected]...
On Sun, 30 Mar 2025 14:54:56 -0400, "Edward Rawde" >>>>>>>>>>>>>>>>>>>>>> <[email protected]d> wrote:
Not long ago JM posted a 1KHz sinewave oscillator with very low distortion.
It used a 470uF non polarized capacitor which in practice would probably be made from two 1000uF capacitors.
There's nothing wrong with that but I wanted to see whether I could make a working circuit without needing
such
a
large
capacitor.
You will need to adjust the feedback to suit. Start with a -5 or -6
gain block after the integrator and adjust it's gain until the startup
is clean (no saturation).
Here's my version of John May's variation. >>>>>>>>>>>>>>>>>>>
Yes, that works but only 120dB down at 4KHz. >>>>>>>>>>>>>>>>>> I put the damping resistor back to 47k since I don't care what happens during the first few seonds as long as it
happens.
If it's necessary to wait one minute for the purest tone, that's fine with me.
Linewraps are going to be a problem - delete all "\n" from the last few lines
You don't want to remove \n just remove the wraps. >>>>>>>>>>>>>>>>>>
BCM61B does not have two independent transistors. >>>>>>>>>>>>>>>>>>
So you probably want BCM847BS which has two independent matched transistors and a very low price at digikey, so
may
as
well
use
two
of them as shown below.
I took the model from
https://github.com/peteut/spice-models/blob/master/nxp/complex_discretes/complex_discretes.txt
It should only be necessary to unwrap the last line of the following.
Don't remove \n just remove the wraps, you may need to use a horizontal scroll bar.
Version 4.1
Best to just offset the integrator output so the amplitude is brought
under control sooner.
Wow. That has much lower distortion too.
If you just replace Q1,2 duals with a simple long tailed pair I think
you will get better performance.
I'm not sure I understand how the multiplier could be implemented with just a long tailed pair.
Just modulate the tail current and select how much to steer to the
output by directly driving the bases rather than indirectly as in your
circuit. The following link shows one example topology, and a four
quadrant differential I/O version. Compare the linearity of each of
them.
https://1drv.ms/u/c/1af24d72a509cd48/EWVCUG7-jFJMu7-01VczCRcBzEC9JPHrV45x7TOunN90Gg?e=GXbvX5
It could be used as shown here.
https://1drv.ms/u/c/1af24d72a509cd48/EVmMVrvUD15GutoR5nCJ7QEBSeZsHWpHudqR0b8XtTLMLw?e=HIV74I
As I've already said, I like it. I've played with it a bit. >>>>>>>>>>>>
The ON-Semiconductor NSS40301MDR2G NPN dual comes with a 2mV guaranteed maximum difference in base-emitter voltages (at
the
same
emitter current). Edward Rawde's Nexperia BCM61B dual part has matched current gain, but no guarantee on the Vbe. The
Nexperia
BCM847BS does offer 2mV base-emitter matching, and would presumably work just as well.
Putting in the ON-Semiconductor dual means that your gain control circuit doesn't have to waste output swing coping with
part-to-part variation.
I've added a cascode transistor (Q1, it should be Q4) to minimise any Early effect distortion.
I've snipped out the op amp driving the base of Q3. Once you'd gone AC-coupled, it wasn't doing anything useful.
And I've put a string of eight diodes in series with R10. They nominally compensate for the temperature dependence
introduced
by
the four rectifier diodes D2, D12, D13 and D14. In this version of the circuit the rectifiers knock about 0.6 volts off
a
sine
wave that peaks at 3.8V, about a quarter of the 15V rail. I haven't run the numbers to fix the best number of diodes,
but
something between six and eight looks okay.
The harmonics aren't great - most of them are about 90dB below the fundamental, but the seventh is only 85dB down.
Not sure I see the point if it's only 80dB down Bill.
@ 7Khz in LTSPice 24.1.5
LTSpice isn't all that reliable as predictor of low level distortion. Having an armoury of different circuits to try when
you
finally get around to building and testing something real may be useful.
I can almost get that from a simple phase shift oscillator and a 1KHz tuned circuit.
I'm sure that you think so. John Larkin thought that a bang-bang amplitude control was worth suggesting...
The last time I included a diode string like that in one of my circuits (which I seem to recall had better than 80dB
performance)
you told me it was nuts.
It probably was. In this case there are better ways of getting a rectified output than a simple series diode - I've posted
circuits which incorporate precision rectifiers which get rid of the forward drop through the diode, and I've built
circuits
that
used synchronous rectifiers built around transmission gates where the output isn't shifted by a temperature dependent
diode
drop.
It went into a GaAs single crystal puller as a retrofit.
The main point of the diode string was as a satirical comment on that aspect of the design you posted, which probably
counts
as
being hostile, but I am hostile to ill-thought out designs, hard though it is to get the design time to sort them out.
I don't see anything particularly hostile there Bill. Just different points of view.
I've got stuck with sorting out other peoples half-baked designs often enough, but only after my bosses had had their
noses
rubbed
in the unfortunate consequences.
When I started work as a fresh graduate (but one who also had practical experience with everything from TV antenna systems
in
hospitals to AY-3-8500 based games) I was amazed at some of the analogue circuit design blunders I encountered.
In one case I built a piece of custom test equipment which needed +15V and -15V. An available transformer had two suitable
isolated
secondary windings so I just used two 7815 devices.
Only to be told by a more experienced "Designer" that connecting the output of a 7815 to ground would short it out and I
had
to
use
7915 for that.....
What he should have said was the you were messing up the ground returns by hooking up the +15V output of the second 7815 to
the
0V
rail.
He was avoiding spending a long time talking about grounding and shielding, which is a rather specialised subject.
I see. Thank you for letting me know what he was thinking Bill.
Do you have some kind of time machine that you travel around in so you can have a better knowledge of what happened in a past
situation when compared with someone who was actually there at the time?
In this particular thread your eight transistor is bonkers, but it >>>>>>>> works - not that I can see how.
Seems pretty obvious to me how it works Bill.
But John May could take out half the transistors and produce a circuit that still worked.
One reason for that is that a current source/sink can be approximated by a high value resistor so instead of using a current
mirror
a single resistor is likely to work fine.
You might need to reverse the polarity of the voltage drive but there are many ways to do that in this circuit.
And you haven't made any attempt to explain how it does work.
As I pointed out some time ago, you never explain how your circuits work Bill.
It's like you just expect others to accept that you have superior knowledge.
If you really could see what other people think then I think you might be surprised at the amount of laughter going on.
You can suspect what you like but that's just another example of you twisting the world into something you would like it to be.
If I didn't know how it was intended to work then it almost certainly would not work.
And suspect that that there were a lot of variations that didn't work >>>>>
Anyone with any understanding of this circuit at all knows that a very basic explanation of how it works is that you need to
multiply the gain control level by a sample of the oscillator signal and feed the result back into the oscillator.
So if your signals are in the form of two currents which never change polarity then a one quadrant current multiplier should
work
fine.
You might then do some research to see if you can find any examples of circuits which meet that requirement.
https://www.google.com/search?q=one+quadrant+analog+current+multiplier&udm=2
Much like you might refer to Horowitz/Hill to see if there are any relevant example circuits.
I'm surprised that you can't see how it works.
I've got a rough idea, but not good enough to let me do anything interesting, or to write any kind of useful explanation of
what
is going on. Writing that kind of explanation is usually a necessary part of getting a circuit into production.
I've yet to see you write an explanation of how a circuit works Bill. >>>>> Instead I've only seen circuits using three or four times as many components as the last one JM posted in this thread and never
any
better than 70dB.
Then you get upset when the rest of the world tries to tell you that although your circuit may have a few good ideas in it,
it's
worthless from a meeting the requirements point of view.
Management needs it before they will spend the extra money on document the design for production, and the final test
technicians
and service engineers need it make sure that the circuit works and to be able to fix it when it doesn't.
John May could see how it worked, and how it could be simplified to four transistors - and eventually down
to two matched pairs.
You seem to be very good at knowing what other people can/could see Bill.
It's a necessary engineering skill. See above.
I prefer not to make any assumptions about what other people can or can't see.
Particularly when I know nothing at all about them other than what has been posted here.
Which you haven't measured on a real circuit yet. Since you don't seem to be all that sensitive to the risks from power supplyHe doesn't like it, and prefers the single
long-tailed pair approach, despite the fact that LTSpice says it >>>>>>>> offers poorer performance.
He provided three examples. All of which obviously work.
The best one from my point of view is the one with lowest distortion. >>>>>>
feedthrough, doing that might be painfully educational
Of course Bill. I have absolutely no doubt that you would take great delight in my pain.
And I have no doubt that you would not offer any meaningful assistance with the power supply design because you would rather
watch
me suffer.
Offering assistance could reduce my suffering which wouldn't do at all. >>>>>
I'd probably use 6V batteries arranged for +/- 18V for a first test of a circuit like this.
With some series components for filtering and to stay below LT1679 36V max.
After all the goal, when I started looking into sinewave oscillators, was to see whether it's really necessary to use
thermistors,
lamps, opto devices or FETs.
Have you come to a conclusion yet? As I seem to have mentioned before, it strikes me that the answer is that it's obvious
necessary.
What's obviously necessary Bill?
The last circuit JM posted has no measurable distortion worth mentioning that I can see.
I like the long-tailed pair approach myself - I can see exactly how it works - but it's probably worth my time to work out
exactly how the four transistor circuit actually works, and why it seems to offer lower distortion in LTSpice simulations.
It's not the kind of project that anybody would fund, >>>>>>>> and the chance that I'd learn anything interesting is remote.
Ah well I'm sorry if you aren't likely to learn anything interesting Bill.
That's text-chopping.
I've learned a lot and will continue to do so.
We can hope.
I'd translate that into "I hope you never learn anything so I can continue to tell you how stupid you are".
That is a remarkably hostile reaction. Most engineers can eventually learn stuff, but some are slower at it than others.
Encouraging the slower ones takes quite a lot of effort because you have to go into quite a lot of detail before you can get the
message across,
I've never seen you explain in any level of detail how your own circuits work Bill.
All explanations are designed to work for the audience they are aimed at. You don't insult the intelligence of people like Phil
Hobbs by going into unnecessary detail. Lesser mortals may well feel short-changed.
I don't speak for Phil Hobbs or anyone else but I think Phil would be impressed with a well thought out highly detailed explanation
of how a circuit works.
He would not be at all insulted no matter what the level of detail was.
On Wed, 9 Apr 2025 11:14:08 -0400, "Edward Rawde"
<[email protected]d> wrote:
"Bill Sloman" <[email protected]> wrote in message news:vt60p8$q8qf$[email protected]...
On 9/04/2025 11:57 pm, Edward Rawde wrote:
"Bill Sloman" <[email protected]> wrote in message news:vt4se2$3qshb$[email protected]...
On 9/04/2025 1:56 am, Edward Rawde wrote:
"Bill Sloman" <[email protected]> wrote in message news:vt2bck$1gmbm$[email protected]...
On 7/04/2025 11:10 pm, Edward Rawde wrote:
"Bill Sloman" <[email protected]> wrote in message news:vsvspr$33gdd$[email protected]...
On 7/04/2025 3:25 am, Edward Rawde wrote:
"Bill Sloman" <[email protected]> wrote in message news:vsuacb$1d4ec$[email protected]...
On 7/04/2025 12:39 am, Edward Rawde wrote:
"Bill Sloman" <[email protected]> wrote in message news:vsu092$14oc7$[email protected]...
On 6/04/2025 2:12 am, JM wrote:
On Fri, 4 Apr 2025 23:55:11 -0400, "Edward Rawde"
<[email protected]d> wrote:
"JM" <[email protected]> wrote in message news:[email protected]...
On Fri, 4 Apr 2025 16:29:27 -0400, "Edward Rawde" >>>>>>>>>>>>>>>> <[email protected]d> wrote:
"JM" <[email protected]> wrote in message news:[email protected]...
On Fri, 4 Apr 2025 14:25:29 -0400, "Edward Rawde" >>>>>>>>>>>>>>>>>> <[email protected]d> wrote:
"Bill Sloman" <[email protected]> wrote in message news:vsnufh$2ou7j$[email protected]...
On 4/04/2025 11:33 am, JM wrote:...
On Thu, 3 Apr 2025 19:25:33 -0400, "Edward Rawde" >>>>>>>>>>>>>>>>>>>>> <[email protected]d> wrote:
"JM" <[email protected]> wrote in message news:[email protected]...
On Sun, 30 Mar 2025 14:54:56 -0400, "Edward Rawde" >>>>>>>>>>>>>>>>>>>>>>> <[email protected]d> wrote: >>>>>>>>>>>>>>>>>>>>>>>
Not long ago JM posted a 1KHz sinewave oscillator with very low distortion.
It used a 470uF non polarized capacitor which in practice would probably be made from two 1000uF capacitors.
There's nothing wrong with that but I wanted to see whether I could make a working circuit without needing
such
a
large
capacitor.
You will need to adjust the feedback to suit. Start with a -5 or -6
gain block after the integrator and adjust it's gain until the startup
is clean (no saturation).
Here's my version of John May's variation. >>>>>>>>>>>>>>>>>>>>
Yes, that works but only 120dB down at 4KHz. >>>>>>>>>>>>>>>>>>> I put the damping resistor back to 47k since I don't care what happens during the first few seonds as long as it
happens.
If it's necessary to wait one minute for the purest tone, that's fine with me.
Linewraps are going to be a problem - delete all "\n" from the last few lines
You don't want to remove \n just remove the wraps. >>>>>>>>>>>>>>>>>>>
BCM61B does not have two independent transistors. >>>>>>>>>>>>>>>>>>>
So you probably want BCM847BS which has two independent matched transistors and a very low price at digikey, so
may
as
well
use
two
of them as shown below.
I took the model from
https://github.com/peteut/spice-models/blob/master/nxp/complex_discretes/complex_discretes.txt
It should only be necessary to unwrap the last line of the following.
Don't remove \n just remove the wraps, you may need to use a horizontal scroll bar.
Version 4.1
Best to just offset the integrator output so the amplitude is brought
under control sooner.
Wow. That has much lower distortion too.
If you just replace Q1,2 duals with a simple long tailed pair I think
you will get better performance.
I'm not sure I understand how the multiplier could be implemented with just a long tailed pair.
Just modulate the tail current and select how much to steer to the
output by directly driving the bases rather than indirectly as in your
circuit. The following link shows one example topology, and a four
quadrant differential I/O version. Compare the linearity of each of
them.
https://1drv.ms/u/c/1af24d72a509cd48/EWVCUG7-jFJMu7-01VczCRcBzEC9JPHrV45x7TOunN90Gg?e=GXbvX5
It could be used as shown here.
https://1drv.ms/u/c/1af24d72a509cd48/EVmMVrvUD15GutoR5nCJ7QEBSeZsHWpHudqR0b8XtTLMLw?e=HIV74I
As I've already said, I like it. I've played with it a bit. >>>>>>>>>>>>>
The ON-Semiconductor NSS40301MDR2G NPN dual comes with a 2mV guaranteed maximum difference in base-emitter voltages (at
the
same
emitter current). Edward Rawde's Nexperia BCM61B dual part has matched current gain, but no guarantee on the Vbe. The
Nexperia
BCM847BS does offer 2mV base-emitter matching, and would presumably work just as well.
Putting in the ON-Semiconductor dual means that your gain control circuit doesn't have to waste output swing coping with
part-to-part variation.
I've added a cascode transistor (Q1, it should be Q4) to minimise any Early effect distortion.
I've snipped out the op amp driving the base of Q3. Once you'd gone AC-coupled, it wasn't doing anything useful.
And I've put a string of eight diodes in series with R10. They nominally compensate for the temperature dependence
introduced
by
the four rectifier diodes D2, D12, D13 and D14. In this version of the circuit the rectifiers knock about 0.6 volts off
a
sine
wave that peaks at 3.8V, about a quarter of the 15V rail. I haven't run the numbers to fix the best number of diodes,
but
something between six and eight looks okay.
The harmonics aren't great - most of them are about 90dB below the fundamental, but the seventh is only 85dB down.
Not sure I see the point if it's only 80dB down Bill.
@ 7Khz in LTSPice 24.1.5
LTSpice isn't all that reliable as predictor of low level distortion. Having an armoury of different circuits to try when
you
finally get around to building and testing something real may be useful.
I can almost get that from a simple phase shift oscillator and a 1KHz tuned circuit.
I'm sure that you think so. John Larkin thought that a bang-bang amplitude control was worth suggesting...
The last time I included a diode string like that in one of my circuits (which I seem to recall had better than 80dB
performance)
you told me it was nuts.
It probably was. In this case there are better ways of getting a rectified output than a simple series diode - I've posted
circuits which incorporate precision rectifiers which get rid of the forward drop through the diode, and I've built
circuits
that
used synchronous rectifiers built around transmission gates where the output isn't shifted by a temperature dependent
diode
drop.
It went into a GaAs single crystal puller as a retrofit. >>>>>>>>>>>
The main point of the diode string was as a satirical comment on that aspect of the design you posted, which probably
counts
as
being hostile, but I am hostile to ill-thought out designs, hard though it is to get the design time to sort them out.
I don't see anything particularly hostile there Bill. Just different points of view.
I've got stuck with sorting out other peoples half-baked designs often enough, but only after my bosses had had their
noses
rubbed
in the unfortunate consequences.
When I started work as a fresh graduate (but one who also had practical experience with everything from TV antenna systems
in
hospitals to AY-3-8500 based games) I was amazed at some of the analogue circuit design blunders I encountered.
In one case I built a piece of custom test equipment which needed +15V and -15V. An available transformer had two suitable
isolated
secondary windings so I just used two 7815 devices.
Only to be told by a more experienced "Designer" that connecting the output of a 7815 to ground would short it out and I
had
to
use
7915 for that.....
What he should have said was the you were messing up the ground returns by hooking up the +15V output of the second 7815 to
the
0V
rail.
He was avoiding spending a long time talking about grounding and shielding, which is a rather specialised subject.
I see. Thank you for letting me know what he was thinking Bill. >>>>>>>> Do you have some kind of time machine that you travel around in so you can have a better knowledge of what happened in a past
situation when compared with someone who was actually there at the time?
In this particular thread your eight transistor is bonkers, but it >>>>>>>>> works - not that I can see how.
Seems pretty obvious to me how it works Bill.
But John May could take out half the transistors and produce a circuit that still worked.
One reason for that is that a current source/sink can be approximated by a high value resistor so instead of using a current
mirror
a single resistor is likely to work fine.
You might need to reverse the polarity of the voltage drive but there are many ways to do that in this circuit.
And you haven't made any attempt to explain how it does work.
As I pointed out some time ago, you never explain how your circuits work Bill.
It's like you just expect others to accept that you have superior knowledge.
If you really could see what other people think then I think you might be surprised at the amount of laughter going on.
You can suspect what you like but that's just another example of you twisting the world into something you would like it to be.
If I didn't know how it was intended to work then it almost certainly would not work.
And suspect that that there were a lot of variations that didn't work >>>>>>
Anyone with any understanding of this circuit at all knows that a very basic explanation of how it works is that you need to
multiply the gain control level by a sample of the oscillator signal and feed the result back into the oscillator.
So if your signals are in the form of two currents which never change polarity then a one quadrant current multiplier should
work
fine.
You might then do some research to see if you can find any examples of circuits which meet that requirement.
https://www.google.com/search?q=one+quadrant+analog+current+multiplier&udm=2
Much like you might refer to Horowitz/Hill to see if there are any relevant example circuits.
I'm surprised that you can't see how it works.
I've got a rough idea, but not good enough to let me do anything interesting, or to write any kind of useful explanation of
what
is going on. Writing that kind of explanation is usually a necessary part of getting a circuit into production.
I've yet to see you write an explanation of how a circuit works Bill. >>>>>> Instead I've only seen circuits using three or four times as many components as the last one JM posted in this thread and never
any
better than 70dB.
Then you get upset when the rest of the world tries to tell you that although your circuit may have a few good ideas in it,
it's
worthless from a meeting the requirements point of view.
Management needs it before they will spend the extra money on document the design for production, and the final test
technicians
and service engineers need it make sure that the circuit works and to be able to fix it when it doesn't.
John May could see how it worked, and how it could be simplified to four transistors - and eventually down
to two matched pairs.
You seem to be very good at knowing what other people can/could see Bill.
It's a necessary engineering skill. See above.
I prefer not to make any assumptions about what other people can or can't see.
Particularly when I know nothing at all about them other than what has been posted here.
Which you haven't measured on a real circuit yet. Since you don't seem to be all that sensitive to the risks from power supplyHe doesn't like it, and prefers the single
long-tailed pair approach, despite the fact that LTSpice says it >>>>>>>>> offers poorer performance.
He provided three examples. All of which obviously work.
The best one from my point of view is the one with lowest distortion. >>>>>>>
feedthrough, doing that might be painfully educational
Of course Bill. I have absolutely no doubt that you would take great delight in my pain.
And I have no doubt that you would not offer any meaningful assistance with the power supply design because you would rather
watch
me suffer.
Offering assistance could reduce my suffering which wouldn't do at all. >>>>>>
I'd probably use 6V batteries arranged for +/- 18V for a first test of a circuit like this.
With some series components for filtering and to stay below LT1679 36V max.
After all the goal, when I started looking into sinewave oscillators, was to see whether it's really necessary to use
thermistors,
lamps, opto devices or FETs.
Have you come to a conclusion yet? As I seem to have mentioned before, it strikes me that the answer is that it's obvious
necessary.
What's obviously necessary Bill?
The last circuit JM posted has no measurable distortion worth mentioning that I can see.
I like the long-tailed pair approach myself - I can see exactly how it works - but it's probably worth my time to work outAh well I'm sorry if you aren't likely to learn anything interesting Bill.
exactly how the four transistor circuit actually works, and why it seems to offer lower distortion in LTSpice simulations.
>>>>>> It's not the kind of project that anybody would fund, >>>>>>>>> and the chance that I'd learn anything interesting is remote. >>>>>>>>
That's text-chopping.
I've learned a lot and will continue to do so.
We can hope.
I'd translate that into "I hope you never learn anything so I can continue to tell you how stupid you are".
That is a remarkably hostile reaction. Most engineers can eventually learn stuff, but some are slower at it than others.
Encouraging the slower ones takes quite a lot of effort because you have to go into quite a lot of detail before you can get the
message across,
I've never seen you explain in any level of detail how your own circuits work Bill.
All explanations are designed to work for the audience they are aimed at. You don't insult the intelligence of people like Phil
Hobbs by going into unnecessary detail. Lesser mortals may well feel short-changed.
I don't speak for Phil Hobbs or anyone else but I think Phil would be impressed with a well thought out highly detailed explanation
of how a circuit works.
He would not be at all insulted no matter what the level of detail was.
Phil is hard to insult with any efficiency. Slam a gin and tonic or
three into him, and it's impossible.
"Bill Sloman" <[email protected]> wrote in message news:vt6f6f$16v37$[email protected]...
On 10/04/2025 1:14 am, Edward Rawde wrote:
"Bill Sloman" <[email protected]> wrote in message news:vt60p8$q8qf$[email protected]...
On 9/04/2025 11:57 pm, Edward Rawde wrote:
"Bill Sloman" <[email protected]> wrote in message news:vt4se2$3qshb$[email protected]...
On 9/04/2025 1:56 am, Edward Rawde wrote:
"Bill Sloman" <[email protected]> wrote in message news:vt2bck$1gmbm$[email protected]...
On 7/04/2025 11:10 pm, Edward Rawde wrote:
"Bill Sloman" <[email protected]> wrote in message news:vsvspr$33gdd$[email protected]...
On 7/04/2025 3:25 am, Edward Rawde wrote:
"Bill Sloman" <[email protected]> wrote in message news:vsuacb$1d4ec$[email protected]...
On 7/04/2025 12:39 am, Edward Rawde wrote:
"Bill Sloman" <[email protected]> wrote in message news:vsu092$14oc7$[email protected]...
On 6/04/2025 2:12 am, JM wrote:
On Fri, 4 Apr 2025 23:55:11 -0400, "Edward Rawde" >>>>>>>>>>>>>>> <[email protected]d> wrote:
"JM" <[email protected]> wrote in message news:[email protected]...
On Fri, 4 Apr 2025 16:29:27 -0400, "Edward Rawde" >>>>>>>>>>>>>>>>> <[email protected]d> wrote:
"JM" <[email protected]> wrote in message news:[email protected]...
On Fri, 4 Apr 2025 14:25:29 -0400, "Edward Rawde" >>>>>>>>>>>>>>>>>>> <[email protected]d> wrote:
"Bill Sloman" <[email protected]> wrote in message news:vsnufh$2ou7j$[email protected]...
On 4/04/2025 11:33 am, JM wrote:...
On Thu, 3 Apr 2025 19:25:33 -0400, "Edward Rawde" >>>>>>>>>>>>>>>>>>>>>> <[email protected]d> wrote:
"JM" <[email protected]> wrote in message news:[email protected]...
On Sun, 30 Mar 2025 14:54:56 -0400, "Edward Rawde" >>>>>>>>>>>>>>>>>>>>>>>> <[email protected]d> wrote: >>>>>>>>>>>>>>>>>>>>>>>>
Not long ago JM posted a 1KHz sinewave oscillator with very low distortion.
It used a 470uF non polarized capacitor which in practice would probably be made from two 1000uF
capacitors.
There's nothing wrong with that but I wanted to see whether I could make a working circuit without needing
such
a
large
capacitor.
You will need to adjust the feedback to suit. Start with a -5 or -6
gain block after the integrator and adjust it's gain until the startup
is clean (no saturation).
Here's my version of John May's variation. >>>>>>>>>>>>>>>>>>>>>
Yes, that works but only 120dB down at 4KHz. >>>>>>>>>>>>>>>>>>>> I put the damping resistor back to 47k since I don't care what happens during the first few seonds as long as it
happens.
If it's necessary to wait one minute for the purest tone, that's fine with me.
Linewraps are going to be a problem - delete all "\n" from the last few lines
You don't want to remove \n just remove the wraps. >>>>>>>>>>>>>>>>>>>>
BCM61B does not have two independent transistors. >>>>>>>>>>>>>>>>>>>>
So you probably want BCM847BS which has two independent matched transistors and a very low price at digikey, so
may
as
well
use
two
of them as shown below.
I took the model from
https://github.com/peteut/spice-models/blob/master/nxp/complex_discretes/complex_discretes.txt
It should only be necessary to unwrap the last line of the following.
Don't remove \n just remove the wraps, you may need to use a horizontal scroll bar.
Version 4.1
Best to just offset the integrator output so the amplitude is brought
under control sooner.
Wow. That has much lower distortion too.
If you just replace Q1,2 duals with a simple long tailed pair I think
you will get better performance.
I'm not sure I understand how the multiplier could be implemented with just a long tailed pair.
Just modulate the tail current and select how much to steer to the
output by directly driving the bases rather than indirectly as in your
circuit. The following link shows one example topology, and a four
quadrant differential I/O version. Compare the linearity of each of
them.
https://1drv.ms/u/c/1af24d72a509cd48/EWVCUG7-jFJMu7-01VczCRcBzEC9JPHrV45x7TOunN90Gg?e=GXbvX5
It could be used as shown here.
https://1drv.ms/u/c/1af24d72a509cd48/EVmMVrvUD15GutoR5nCJ7QEBSeZsHWpHudqR0b8XtTLMLw?e=HIV74I
As I've already said, I like it. I've played with it a bit. >>>>>>>>>>>>>>
The ON-Semiconductor NSS40301MDR2G NPN dual comes with a 2mV guaranteed maximum difference in base-emitter voltages
(at
the
same
emitter current). Edward Rawde's Nexperia BCM61B dual part has matched current gain, but no guarantee on the Vbe. The
Nexperia
BCM847BS does offer 2mV base-emitter matching, and would presumably work just as well.
Putting in the ON-Semiconductor dual means that your gain control circuit doesn't have to waste output swing coping
with
part-to-part variation.
I've added a cascode transistor (Q1, it should be Q4) to minimise any Early effect distortion.
I've snipped out the op amp driving the base of Q3. Once you'd gone AC-coupled, it wasn't doing anything useful.
And I've put a string of eight diodes in series with R10. They nominally compensate for the temperature dependence
introduced
by
the four rectifier diodes D2, D12, D13 and D14. In this version of the circuit the rectifiers knock about 0.6 volts
off
a
sine
wave that peaks at 3.8V, about a quarter of the 15V rail. I haven't run the numbers to fix the best number of diodes,
but
something between six and eight looks okay.
The harmonics aren't great - most of them are about 90dB below the fundamental, but the seventh is only 85dB down.
Not sure I see the point if it's only 80dB down Bill. >>>>>>>>>>>>> @ 7Khz in LTSPice 24.1.5
LTSpice isn't all that reliable as predictor of low level distortion. Having an armoury of different circuits to try
when
you
finally get around to building and testing something real may be useful.
I can almost get that from a simple phase shift oscillator and a 1KHz tuned circuit.
I'm sure that you think so. John Larkin thought that a bang-bang amplitude control was worth suggesting...
The last time I included a diode string like that in one of my circuits (which I seem to recall had better than 80dB
performance)
you told me it was nuts.
It probably was. In this case there are better ways of getting a rectified output than a simple series diode - I've
posted
circuits which incorporate precision rectifiers which get rid of the forward drop through the diode, and I've built
circuits
that
used synchronous rectifiers built around transmission gates where the output isn't shifted by a temperature dependent
diode
drop.
It went into a GaAs single crystal puller as a retrofit. >>>>>>>>>>>>
The main point of the diode string was as a satirical comment on that aspect of the design you posted, which probably
counts
as
being hostile, but I am hostile to ill-thought out designs, hard though it is to get the design time to sort them out.
I don't see anything particularly hostile there Bill. Just different points of view.
I've got stuck with sorting out other peoples half-baked designs often enough, but only after my bosses had had their
noses
rubbed
in the unfortunate consequences.
When I started work as a fresh graduate (but one who also had practical experience with everything from TV antenna
systems
in
hospitals to AY-3-8500 based games) I was amazed at some of the analogue circuit design blunders I encountered.
In one case I built a piece of custom test equipment which needed +15V and -15V. An available transformer had two
suitable
isolated
secondary windings so I just used two 7815 devices.
Only to be told by a more experienced "Designer" that connecting the output of a 7815 to ground would short it out and I
had
to
use
7915 for that.....
What he should have said was the you were messing up the ground returns by hooking up the +15V output of the second 7815
to
the
0V
rail.
He was avoiding spending a long time talking about grounding and shielding, which is a rather specialised subject.
I see. Thank you for letting me know what he was thinking Bill. >>>>>>>>> Do you have some kind of time machine that you travel around in so you can have a better knowledge of what happened in a
past
situation when compared with someone who was actually there at the time?
In this particular thread your eight transistor is bonkers, but it >>>>>>>>>> works - not that I can see how.
Seems pretty obvious to me how it works Bill.
But John May could take out half the transistors and produce a circuit that still worked.
One reason for that is that a current source/sink can be approximated by a high value resistor so instead of using a current
mirror
a single resistor is likely to work fine.
You might need to reverse the polarity of the voltage drive but there are many ways to do that in this circuit.
And you haven't made any attempt to explain how it does work.
As I pointed out some time ago, you never explain how your circuits work Bill.
It's like you just expect others to accept that you have superior knowledge.
If you really could see what other people think then I think you might be surprised at the amount of laughter going on.
You can suspect what you like but that's just another example of you twisting the world into something you would like it to
If I didn't know how it was intended to work then it almost certainly would not work.
And suspect that that there were a lot of variations that didn't work >>>>>>>
be.
Anyone with any understanding of this circuit at all knows that a very basic explanation of how it works is that you need to
multiply the gain control level by a sample of the oscillator signal and feed the result back into the oscillator.
So if your signals are in the form of two currents which never change polarity then a one quadrant current multiplier should
work
fine.
You might then do some research to see if you can find any examples of circuits which meet that requirement.
https://www.google.com/search?q=one+quadrant+analog+current+multiplier&udm=2
Much like you might refer to Horowitz/Hill to see if there are any relevant example circuits.
I'm surprised that you can't see how it works.
I've got a rough idea, but not good enough to let me do anything interesting, or to write any kind of useful explanation of
what
is going on. Writing that kind of explanation is usually a necessary part of getting a circuit into production.
I've yet to see you write an explanation of how a circuit works Bill. >>>>>>> Instead I've only seen circuits using three or four times as many components as the last one JM posted in this thread and
never
any
better than 70dB.
Then you get upset when the rest of the world tries to tell you that although your circuit may have a few good ideas in it,
it's
worthless from a meeting the requirements point of view.
Management needs it before they will spend the extra money on document the design for production, and the final test
technicians
and service engineers need it make sure that the circuit works and to be able to fix it when it doesn't.
John May could see how it worked, and how it could be simplified to four transistors - and eventually down
to two matched pairs.
You seem to be very good at knowing what other people can/could see Bill.
It's a necessary engineering skill. See above.
I prefer not to make any assumptions about what other people can or can't see.
Particularly when I know nothing at all about them other than what has been posted here.
Which you haven't measured on a real circuit yet. Since you don't seem to be all that sensitive to the risks from powerHe doesn't like it, and prefers the single
long-tailed pair approach, despite the fact that LTSpice says it >>>>>>>>>> offers poorer performance.
He provided three examples. All of which obviously work.
The best one from my point of view is the one with lowest distortion. >>>>>>>>
supply
feedthrough, doing that might be painfully educational
Of course Bill. I have absolutely no doubt that you would take great delight in my pain.
And I have no doubt that you would not offer any meaningful assistance with the power supply design because you would rather
watch
me suffer.
Offering assistance could reduce my suffering which wouldn't do at all. >>>>>>>
I'd probably use 6V batteries arranged for +/- 18V for a first test of a circuit like this.
With some series components for filtering and to stay below LT1679 36V max.
After all the goal, when I started looking into sinewave oscillators, was to see whether it's really necessary to use
thermistors,
lamps, opto devices or FETs.
Have you come to a conclusion yet? As I seem to have mentioned before, it strikes me that the answer is that it's obvious
necessary.
What's obviously necessary Bill?
The last circuit JM posted has no measurable distortion worth mentioning that I can see.
I like the long-tailed pair approach myself - I can see exactly how it works - but it's probably worth my time to work outAh well I'm sorry if you aren't likely to learn anything interesting Bill.
exactly how the four transistor circuit actually works, and why it seems to offer lower distortion in LTSpice simulations.
>>>>>> It's not the kind of project that anybody would fund, >>>>>>>>>> and the chance that I'd learn anything interesting is remote. >>>>>>>>>
That's text-chopping.
I've learned a lot and will continue to do so.
We can hope.
I'd translate that into "I hope you never learn anything so I can continue to tell you how stupid you are".
That is a remarkably hostile reaction. Most engineers can eventually learn stuff, but some are slower at it than others.
Encouraging the slower ones takes quite a lot of effort because you have to go into quite a lot of detail before you can get
the
message across,
I've never seen you explain in any level of detail how your own circuits work Bill.
All explanations are designed to work for the audience they are aimed at. You don't insult the intelligence of people like Phil
Hobbs by going into unnecessary detail. Lesser mortals may well feel short-changed.
I don't speak for Phil Hobbs or anyone else but I think Phil would be impressed with a well thought out highly detailed
explanation
of how a circuit works.
In the appropriate context. Sci.electronics.design has tended to brevity over the twenty-odd years I've been posting here and
following the posts.
He would not be at all insulted no matter what the level of detail was.
The phrase "insult the intelligence" doesn't refer to be people feeling insulted - rather to them being bored by unnecessary
detail. He probably wouldn't feel insulted but he'd probably skip most of the detail.
The reference to explanations in different contexts doesn't seem to have registered with you.
LOL. You can't skip detail which isn't there.
You can certainly tailor your approach to the individual you're dealing with Bill.
But it looks to me that you would rather tailor your approach in such a way as to make the other person appear as much of a "Lesser
mortal" (your words) as possible.
Have you looked at JM's latest post (2:06 PM on the 9th) which demonstrates the sample & hold method?
Do you still think it's "Very funny" (Your words in your own thread on 6th February).
What are you doing up at 5 AM anyway?
I wasn't able to reply directly to Bill Soman's post 10th April 6:33 AM due to error 411 header too long.
However I just wanted to address the following:
"Sample and holds necessarily put switching spikes into the power supply >rails. Decoupling the relevant bits from the rails can minimise the >consequences, but if you are aiming for harmonics 120dB below the >fundamental, you have to decouple a lot of routes rather carefully."
"Somebody like you who doesn't like ferrite beads and ferrite chips
wouldn't enjoy that."
You really are a complete idiot Bill.
On Thu, 10 Apr 2025 17:27:46 -0400, "Edward Rawde"
<[email protected]d> wrote:
I wasn't able to reply directly to Bill Soman's post 10th April 6:33 AM due to error 411 header too long.
However I just wanted to address the following:
"Sample and holds necessarily put switching spikes into the power supply >>rails. Decoupling the relevant bits from the rails can minimise the >>consequences, but if you are aiming for harmonics 120dB below the >>fundamental, you have to decouple a lot of routes rather carefully."
"Somebody like you who doesn't like ferrite beads and ferrite chips >>wouldn't enjoy that."
You really are a complete idiot Bill.
Ed, DO NOT FEED THE TROLL
Joe
I wasn't able to reply directly to Bill Soman's post 10th April 6:33 AM due to error 411 header too long.
However I just wanted to address the following:
"Sample and holds necessarily put switching spikes into the power supply rails. Decoupling the relevant bits from the rails can minimise the consequences, but if you are aiming for harmonics 120dB below the fundamental, you have to decouple a lot of routes rather carefully."
"Somebody like you who doesn't like ferrite beads and ferrite chips
wouldn't enjoy that."
You really are a complete idiot Bill.
"Joe Gwinn" <[email protected]> wrote in message news:[email protected]...
On Thu, 10 Apr 2025 17:27:46 -0400, "Edward Rawde"
<[email protected]d> wrote:
I wasn't able to reply directly to Bill Soman's post 10th April 6:33 AM due to error 411 header too long.
However I just wanted to address the following:
"Sample and holds necessarily put switching spikes into the power supply >>> rails. Decoupling the relevant bits from the rails can minimise the
consequences, but if you are aiming for harmonics 120dB below the
fundamental, you have to decouple a lot of routes rather carefully."
"Somebody like you who doesn't like ferrite beads and ferrite chips
wouldn't enjoy that."
You really are a complete idiot Bill.
Ed, DO NOT FEED THE TROLL
Yeah you're right. I am done with Bill.
How about using a DAC driven from a uC, or even some clever bit of
hardware?
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