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Transimpedance Considerations for High Speed Amplifiers - Application Report SBOA122

Karen
Intellectual 940 points
Other Parts Discussed in Thread: OPA657, TINA-TI

Designing for high-resolution detection circuits using photodiodes?  See the new Application Report  "Transimpedance Considerations for High-Speed Amplifers" by Xavier Ramus.  

sboa122 - Transimpedance.pdf
  • 0
    Prodigy 210 points

    Hi Xavier,

    Thanks for your reply. I really need to apologise for posting in this thread. I should have started a new thread in the forum. Sorry about it.

    The photodiode capacitance will range from 3.5pF to 280pF. The main reason for this wide range of photodiode capacitance is due to the difference in active area of photodiode we are using and the reverse bias voltage applied to it. Next, we are targeting to achieve 100MHz bandwidth and at 60dB gain. (Note: I have used TI OPA657 and the results are great for lower diode capacitance)

    I read and try the idea of using a BJT to isolate the summing junction across the OPAMP from the diode capacitance. However, the results that I got from TINA-TI simulation were not that good.

    Are there any suggestions that you can provide me?

    Thanks.

    Cheers,

    Wilson

     

  • 0 in reply to Wilson Teo
    TI__Expert 4950 points

    Hi Wilson,

    I was not able to make a boostrapping technique worked, but I did find a potential solution by using a composite amplifier.  See attached TINA file.

    Best regards,

    Xavier

    OPA657+OPA695 composite circuit.zip
  • 0 in reply to Xavier Ramus
    Prodigy 210 points

    Hi Xavier,

    Ok.. Thanks for your help. =)