OP Amp analysis. I had this thrown at me and I have very little idea what is how to go about solving

Thread Starter


Joined Apr 29, 2016
Here's what I know. The circuit is measuring the current of a laser diode using a current mirror. for the analysis to make things easy assume 100ma is entering the system. I get confused about how the currents run through the circuit. I'm pretty sure the first op amp has a gain of -3.0. besides this I have no idea how to go about solving the gain of the second op amp etc. This all interfaces to a hotmux data logger that can handle a voltage of 0-50mv.

I hope this is enough info. also Stepping through this would be fantastic.

Thank you



Joined Feb 24, 2006
I can't help you if I can't read your schematic. That is perhaps the worlds' worst uploaded image. Do you seriously believe we can help if you feed us garbage like that?


Joined Sep 9, 2010
Huh, I can read it OK once I click to get the full resolution.

What I'm missing is the question, the goal.

One thing I can tell you is that you don't have 100mA flowing in the circuit as shown. There's nowhere for it to go. I see 90kΩ plus a diode for the path of least resistance.