Op amp troubleshooting

Thread Starter


Joined 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!


Joined 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?


Joined 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