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Original question:

Charge Sensitive Preamplifier Op-amp Selection

OPA357: Charge amplifier design

danielb
Prodigy 120 points
Other Parts Discussed in Thread: OPA357, LMH34400

Tool/software:

I would like to design a charge amplifier for a sensor with 1nF and 200MOhms and bias voltage 30V. Sensor current is around 1 mA. This is the circuit I have now:

My output is a strange:

I have tested several parameters to get a better output, but without success. Any suggestion on how to improve this?

CSA-SiPM-OPA357.tsc

  • 0
    Prodigy 120 points

    By the way, is this a good amp op for this application?

  • 0 in reply to danielb
    TI__Genius 13140 points

    Hello Daniel,

    Myself and the HSAMPS team are going to work on this for you, I do apologize for not having a response to you earlier.  We had a mix of project priority changes and team members out-of-office.

    To help clarify and understand, are you using the OPA357 as a transimpedance amplifier (TIA) for a SiPM (silicon photo multiplier)?

    We do have our OPA85x discrete family of TIAs, as well as our integrated TIAs (LMH3240x & LMH34400) for optical applications.  The OPA357 may be adequate here too, but I wanted to give you some ideas while we work on a solution.

    Best,

    Alec

  • 0 in reply to Alec Saebeler
    Prodigy 120 points

    Dear Alec,

    Thank you for your reply. I would to use the OPA357 as a charge amplifier for a SiPM. It is not a TIA. I checked the op amps you mentioned, but the consume a lot of current. Does the current source I used is a good representation of a SiPM?

  • 0 in reply to danielb
    TI__Genius 13140 points

    Hello Daniel,

    Thank you for clarifying.  Let me check with my team on part recommendations (or keeping OPA357) as well as how to model a SiPM.

    I will update you tomorrow.

    Best,

    Alec

  • 0 in reply to Alec Saebeler
    TI__Genius 13140 points

    Hello Daniel,

    Do you know if you will be using the fast output of the SiPM, which is a voltage signal, or the current output of the SiPM for your design?

    Best,

    Alec

  • 0 in reply to Alec Saebeler
    Prodigy 120 points

    Dear Alec,

    We will use the current output of the SiPM. Thanks!

  • 0 in reply to danielb
    TI__Genius 13140 points

    Hello Daniel,

    I overlooked an aspect of your circuit in my previous messages.  With a feedback resistor setting the transimpedance gain of 1MOhm (one megaOhm), your current of 10mA would result in a voltage of 2kV (two kilovolts)!!

    This will not work and will certainly result in a broken amplifier.  I think reviewing your SiPM datasheet and adjusting to a smaller Rf resistor and Cf capacitor would help your design.

    Please let me know if you need further support.

    Best,

    Alec

  • 0 in reply to Alec Saebeler
    Prodigy 120 points

    But this should be a charge amplifier, not a transimpedance. How should I correct the circuit to operate as a charge amplifier?