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OPA207: best solution to read 200pA AC or 100nV AC

Part Number: OPA207
Other Parts Discussed in Thread: OPA140, OPA828, OPA197

Hi Team,

I received the following request, can you suggest me the best device?

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We are looking for a solution to read about 200pA AC current with TIA or 100nV AC voltage with instrumentation amplifier.

We need to amplify these signals to 5mV AC.

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Regards,

Fabio

  • Hello Fabio, can't really answer wisely without target F-3dB and perhaps a noise or DC precision target. May not be too critical on that as he says AC.

    This is a 10Mohm transimpedance gain, so FET input probably desired - to solve for the required GBP, would also need the capacitance looking back to the source.
  • Hi Fabio,

    what is the signal? And where is it from? A sensor? A bridge? What is the source resistance?

    Why is it current "or" voltage?

    We need much much more details...

    Kai
  • Hello Fabio,

    Regarding your inquiry:

    We are looking for a solution to read about 200pA AC current with TIA or 100nV AC voltage with instrumentation amplifier. We need to amplify these signals to 5mV AC.

    If your preference is to convert the 200 pA input current to a 5 mV output voltage, then a low-input current op amp could be applied as a TIA. A CMOS, or JFET input op amp having low input bias current (Ib) would be a good choice. Here are some JFET and CMOS op amps that feature high electrical performance and low Ib:

    OPA140    Ib  = 10 pA max at 25C

    OPA828    Ib = 5 pA max at 25C

    OPA197    Ib  = 20 pA max at 25 C

    All of all these op amps have very low voltage noise performance. You can view their datasheets here:

    Regards, Thomas

    Precision Amplifiers Applications Engineering

  • Thanks Thomas,
    Should be more than enough for the moment.

    Regards,
    Fabio