I have put some on an amplifier box for my + and 5 V supplies. But yet a ripple on either supply signically contaminates my outut signal.
AFAIK they represent a 6-uH series inductor and an about 5-nF parallel capacitor. Is this inductor a coil or a toroid? If it is a coil it could radiate a signficant magnetic field, contaminating my input signal.
Regards
On Thu, 30 Jan 2025, piglet wrote:
You haven’t said what the frequency is of the ripple that you observe,
those devices will have negligible effect at powerline frequency.
Typically 5 to 20 MHz.
You haven�t said what the frequency is of the ripple that you observe,
those devices will have negligible effect at powerline frequency.
I have put some on an amplifier box for my + and 5 V supplies. But yet a >ripple on either supply signically contaminates my outut signal.
AFAIK they represent a 6-uH series inductor and an about 5-nF parallel >capacitor. Is this inductor a coil or a toroid? If it is a coil it could >radiate a signficant magnetic field, contaminating my input signal.
Regards
EMI filters only filter high frequency stuff, AM band and up. If your
problem is AC-line frequency ripple or low frequency switcher noise, a typical EMI filter won'[t help.
What does the contamination look/sound like?
Ok, thanks. I’d expect they’d be very effective at VHF/UHF but should already be showing some insertion loss by 5MHz
On Thu, 30 Jan 2025, john larkin wrote:
EMI filters only filter high frequency stuff, AM band and up. If your
problem is AC-line frequency ripple or low frequency switcher noise, a
typical EMI filter won'[t help.
What does the contamination look/sound like?
At 10 MHz the ripple of my power supplies contaminates my output signal
at a level much higher than the documented inserson loss.
So I suspect some 10 MHz makes its way through a magnetic field and
perhaps a filter with only a simple annular capacitor would be more effective.
On 1/31/25 15:40, Jean-Pierre Coulon wrote:
On Thu, 30 Jan 2025, john larkin wrote:
EMI filters only filter high frequency stuff, AM band and up. If your
problem is AC-line frequency ripple or low frequency switcher noise, a
typical EMI filter won'[t help.
What does the contamination look/sound like?
At 10 MHz the ripple of my power supplies contaminates my output signal
at a level much higher than the documented inserson loss.
So I suspect some 10 MHz makes its way through a magnetic field and
perhaps a filter with only a simple annular capacitor would be� more
effective.
It looks like your circuit has gain from power-in to output. That's
bad.
Anyway, it's poor practice to expect a feedthrough filter to clean
switcher noise off your power lines.
Jeroen Belleman <[email protected]> wrote:
On 1/31/25 15:40, Jean-Pierre Coulon wrote:
On Thu, 30 Jan 2025, john larkin wrote:
EMI filters only filter high frequency stuff, AM band and up. If your
problem is AC-line frequency ripple or low frequency switcher noise, a >>>> typical EMI filter won'[t help.
What does the contamination look/sound like?
At 10 MHz the ripple of my power supplies contaminates my output signal
at a level much higher than the documented inserson loss.
So I suspect some 10 MHz makes its way through a magnetic field and
perhaps a filter with only a simple annular capacitor would be?
effective.
It looks like your circuit has gain from power-in to output. That's
bad.
Anyway, it's poor practice to expect a feedthrough filter to clean
switcher noise off your power lines.
Common in single-ended circuits, though. I do a lot of discrete amps and
(for my sins) photoreceivers, which use two-transistor, four-pole cap >multipliers with >>100 dB rejection at SMPS frequencies.
Cheers
Phil Hobbs
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