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

    Active 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

    AAC Fanatic!

    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