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Op amp troubleshooting

Discussion in 'General Electronics Chat' started by sdh314, Nov 28, 2011.

  1. sdh314

    Thread Starter New Member

    Jun 2, 2011
    Hi all,

    I've got a simple photodiode transimpedance circuit: photodiode cathode connected to the inverting input, non-inverting input & PD anode to ground, and a 1Meg feedback resistor.

    I'm not getting the results I expect, and I have a feeling the op-amp may be busted. What is the best way to test this? My first thoughts are to check that the op-amp inputs be at a similar potential - which they're not (the neg input is at about half a volt). What are other ways to troubleshoot a possibly busted op-amp?

    Thanks in advance!
  2. jimkeith

    Well-Known Member

    Oct 26, 2011
    Probably your ambient light is forcing the op amp into saturation--what is the output doing? What does it do in the dark?
  3. thatoneguy


    Feb 19, 2009
    What is your power supply and which op amp are your using?

    A more complicated circuit is Here, (scroll down) which biases the diode, leaving you with less noise and 1V/uA