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INA2137 LF noise on output

Peter Hanes
Prodigy 25 points
Other Parts Discussed in Thread: INA2137

Hi, I'm using the INA2137 on an analogue audio A-D board.  The device seems to be picking up / generating LF noise on the output at around 10Hz.  Schematic attached, any advice on this appreciated.

Thanks,

Pete

  • 0
    TI__Genius 12325 points

    Hi Peter,

    Do you have an oscilloscope screenshot of this noise? Also, where is this 10Hz noise being measured from, is it directly at the output of the INA2137 (it looks like there are two monitor outputs at these points) or after the op amps?

  • 0 in reply to John Caldwell
    Prodigy 25 points

    Hi John,

    Thanks for looking at this.  Unfortunately i'm not able to see any LF noise on an oscilloscope.  The op-amp filter circuit feeds into an A-D (CS5368) and using an FPGA to convert to AES.  I'm using a PC based AES  FFT audio analyzer.

    With INA2137 output caps removed (C201 and C200,  INA2137 out of circuit)  I'm not seeing any LF noise. 

    The circuit also seems to be microphonic if you tap anywhere on the PCB.

    Please see attached FFT plots.  Is it possible to contact you outside the forum so i can send over the complete schematics etc?

    Thanks,

    Peter

    6177.LF Noise plots.pdf

  • 0 in reply to Peter Hanes
    TI__Genius 12325 points

    Peter,

    I've sent you a friend request on here, once you accept I can message my email address to you and we can communicate that way. 

  • 0 in reply to John Caldwell
    TI__Genius 12325 points

    You should have a message with my email. You can send documents to that address.