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I am using the S12053-02 APD and the ADA4817 op amp. I'm not really sure if I'm getting the correct output or if the configuration I have is the best. I am trying to get a near 1 to 10 nA to mV, so if the APD is measuring 80nA the op amp should output 800mV. I have this circuit breadboarded at the moment and hooked up to an oscilloscope, and so far it is behaving like the LT.SPice sim. Any thoughts?

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  • \$\begingroup\$ The schematic is a little messy. But I recognize it. I think the datasheet makes note of the fact that the input bias currents are in the vicinity of your I2 source, though. Perhaps more than an order of magnitude higher, over operating range. Is that the low end of what you actually need to observe? How/why did you select the 2.5 pA in your schematic? \$\endgroup\$
    – periblepsis
    Commented Sep 20, 2023 at 0:06
  • \$\begingroup\$ Hamamatsu's technical note Si photodiodes (hamamatsu.com/content/dam/hamamatsu-photonics/sites/documents/…) presents a number of examples showing how the user can connect a Si photodiode and opamp (Section 3 How to use, subsections 3-1 Connection to an opamp and 3-2 Application circuit examples). \$\endgroup\$
    – V.V.T
    Commented Sep 20, 2023 at 6:15
  • \$\begingroup\$ What makes this document especially suited to your needs, is that the recommendations on PhD-opamp connection are organized around applications for which the setup is to be designed, as ultra-low-light detection circuit, light-level integration circuit, illuminometer, absortionmeter etc. First study this document, then select the most appropriate prototype, and start your design job with adapting the example circuit to your specific task. If the question arises in the course of this work, I promise it will invite useful answers from experts. \$\endgroup\$
    – V.V.T
    Commented Sep 20, 2023 at 6:15
  • \$\begingroup\$ @periblepsis 2.5nA is within the range of the dark current min and max of the APD (.2nA and 5nA). I need it to be sensitive, so far from what the real circuit is outputting it seems to be doing so. So if I cover the APD with a dark cloth or shut off the room lights, 25mV is what the op amp is outputting, so that means that the APD is reading 2.5nA, theoretically \$\endgroup\$
    – nano_mike2
    Commented Sep 20, 2023 at 14:47
  • \$\begingroup\$ @V.V.T thanks for the document, I'll read up on it and report back! \$\endgroup\$
    – nano_mike2
    Commented Sep 20, 2023 at 14:47

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