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inverting OpAmp Current to volt, when non inverting input is not at GND??

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If the cell is totally in the dark, then any current you measure is leakage current. You can then subtract that from the current when the cell is illuminated to get the current due to the light.
 
You never really answered the questions about bandwidth, static or dynamic measurement etc. It's very tough designing at this level. If I understand it correctly, the 100K resistor will dominate. So, it almost looks like a voltage divider. As resistors get bigger, the noise voltage also gets bigger.

Another way of measuring very small currents is to measure charge, I did that too, but you have to select the mode, wait for things to settle ansd then zero and then count coulombs for say 30 sec or 1 minute and divide by the time.

You have to null. Read this: **broken link removed**

Look very closely at figure 1-26. Note the zero check function. Which basically shorts out the feedback resistor.When you do that, you basically get a voltage follower. If you short the input, you either get a "mess" or if done properly a way to measure Vos. Without some sort of series resistor in the inverting and non-inverting inputs, the output will try to saturate. a few mV across nearly zero ohms is a BIG number. The series resistor protects the OP amp.

With a little more work, you can add gain.

Of, course an automatic zeroing function would be better,

If this is part of say a QE system where your trying to measure the spectral response of the diode, a lock in and a monochometer would be the way to go. That's why I'm asking about particulars.
 
Hello,

Can you use a dual ended output or do you really need a single ended output?
 
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