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PCM1861: Does pcm1861 need input driving ?

Part Number: PCM1861

hi i'm wondering if the pc1861 need input driving, i'm connecting a analog microphone...if it does need, what op amps should i use\

  • Hi, Timotei,

    The PCM1861 is able to drive analog mic inputs directly as it features an integrated PGA in the front-end. There is no need to use an external microphone driver stage as the PGA in the device should be able to increase the mic signal level to the desired line level.

    Best Regards,

      -Diego Meléndez López
       Audio Applications Engineer

  • In reply to Diego Melendez:

    hi,
    thanks for your reply...i found this schematic on the forum i was wondering why is he using a opa1602 to drive the input?...and maybe this is a stupid question but what role those capacitors on avdd pin and the ferrite(100n and 10u), are those decoupling caps?....
  • In reply to Timotei Fogorosiu:

    Hi, Timotei,

    It seems the schematic you are mentioning was not uploaded, so I cannot see it. If an OpAmp is used before the inputs of the PCM1861, probably the signal was conditioned to make it compliant with the device input specs. AS I cannot see the schematic, I am not sure about the function of caps you mention, but based on the values they should be decoupling caps. 

    Best Regards,

      -Diego Meléndez López
       Audio Applications Engineer

  • In reply to Diego Melendez:

    7870.schemat2.pdfhi sorry i forgot to attach the schematic...

  • In reply to Timotei Fogorosiu:

    Hi, Timotei,

    Thanks for sharing the schematic. I think for that particular application the OpAmp is used to condition the input signal, which is not required as long as your input signal is compliant with the device specs. For microphone usage,  no pre-amplifier is needed as the PCM1861 has an internal PGA in the front-end.

    Regarding the ferrite and caps from your question, effectively those are decoupling caps but the circuit connection is incorrect, the caps should be directly tied to the device pin. The ferrite can be connected after the caps to the power supply to filter noise from the main supply.

    Best Regards,

      -Diego Meléndez López
       Audio Applications Engineer

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