I'm working with ICL7650S(online datasheet). Today, when I was working with the Op-Amp, I came across to an odd thing. this is my circuit:
simulate this circuit – Schematic created using CircuitLab
Note that 22uF is for reducing the supply osilation(this question might help you that why I put this cap. also at first I used 100nF and it was getting better and when I changed it to 22uF, the output just 10mv increased(a bit better than earlier)).
The problem is that the Gain isn't correct and especially when I reduce the input, the Gain is going to be reduced(due to the input). for example look at this table:
This table is an example of my measurements(from above circuit). the gain for this circuit should be (357/1.033)+1=346.59
The question is Why the Gain is reducing due to the input?
P.S. A not-completely relevant question. How can I smooth the output of my switching supply as possible as?
Best Answer
You're trying to operate this amplifier very close to its negative supply rail, and it really isn't optimized for that. If you want accurate results near 0V input and output, you need to connect the -V supply pin to a source of -5V.