analoggaininput-offset-voltageoperational-amplifier
I wonder, how to affect the input offset voltage of inverting amplifier when it's output in saturation?
I'm changing gain with decreasing the value of R2. When the gain is greater than 5, output in saturation. But after that point the negative input voltage of opamp also increase with gain increasing.
I cannot limit the value of R2, in this case, how to avoid increasing this offset voltage?
Beacuse I am using virtual ground property of OPAMPs. This offset undesirable for me.
The simplest way to eliminate your problem is to reduce the effective impedance of the source, and a voltage follower will do nicely
simulate this circuit – Schematic created using CircuitLab
The choice of buffer op amp is left to you, depending on the frequency response you need.
I think I found the reason why. It was because the equation should actually be:
V(vout)/(V(+vin)+0.0009999843)
Where the input offset voltage is -0.0009999843V.
This should be subtracted from the Vin and plot becomes better around with a gain of 200K:
Best Answer
The offset voltage is intrinsic to the opamp circuit, every opamp has an offset voltage. If you want to change the offset then the way to do that is with a different opamp. You will never find an op amp that can have both both inputs be the same value, you can find different op amps with lower offsets like auto zero op amps.
The offset voltage is not contributing to your saturation problem. It is offsetting the ground voltage on the negative terminal by -22uV, even with 5x gain, you'll have 220uV contribution on the output.
The saturation is happening because you are gaining 1V by 5x . 1V x 5 is 5V and that will saturate the op amp. So you can either reduce the gain, or increase the rails if you don't want saturation.