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Transimpedance amplifier APD bias

Steven Ho
Prodigy 40 points
Other Parts Discussed in Thread: OPA656

Hi I am working with a Transimpedance Amplifier with a Avalanche Photodiode input for a Laser rangefinder application, like the one shown in the picture. I need help with how to safely bias the APD without damaging the Amplifier as well as not degrading the bandwidth of the circuit. I'm needing to bias the APD at around 100V so that it operates in avalanche breakdown, do I need to put in a resistor somewhere to limit the current so it doesn't damage the Op Amp. 

I'm using the OPA656 op amp, and a 15pF photodiode the hamamatu S12053-10. 

 

  • 0
    TI__Mastermind 22825 points

    Hi Steven,

    I don't think you need to limit the current when you apply 100V reverse bias to your APD. This Hamamatsu plot shows that you'll have less than 50pA dark current:

    The APD current won't flow to the op amp input terminal anyway (it is sourced by the output pin) and you don't have anything to worry about (except may be possibility of electrical shock from the high potential). You may also have to use special techniques to avoid current flow through your PCB dielectric material.

    Regards,

    Hooman