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LME49720 Noise and RFI

Wes Young
Prodigy 30 points

Hello,

I'm working on a prototype audio amplifier that uses LME49720s, but the circuit seems to be picking up RFI. Whenever my wifi base station is switched on, the noise floor looks like the image below. I've attached the schematic so you can see what I've got so far.

Things I've tried are:

Adding 100R in series with the power rails immediately prior to the decoupling.

Shorting R18 and R19 to run at unity gain

Grounding the non-inverting inputs

Cutting the traces to the potentiometer at the output to limit noise being picked up that way.

Any idea what I should try next? Any help or ideas are much appreciated.

Many thanks in advance,

Wes

  • 0
    TI__Guru**** 189399 points

    Hi, Wes,

    Sorry for the delay in getting back to you.

    This is, indeed, very tricky. My favorite solution is to have a fully differential signal path so you can common-mode out all the RFI signal.

    I have also seen people sprinkle caps around 15-33 pF to try and trap the offending signal.

    This is pretty tough to fix...

    -d2