When it comes to measuring CMRR of an analog circuit, how should I proceed?

[Msmatrixin]

If i am in process of making an analog circuit which houses ADC and op-amp, how do i calculate the overall CMRR of that circuit.? I believe the circuit design affects/degrades the value of CMRR, so I am in a process of calculating CMRR at every stage(at amp stage, then at ADC Stage, then the next stage). Is it the right approach? Searched lot of content online, couldnt find anything useful

 

[FvM]

I am in a process of calculating CMRR at every stage(at amp stage, then at ADC Stage, then the next stage). Is it the right approach?

Certainly not. CMRR is a property of a differential input stage, it makes no sense in general to determine it for internal stages.

 

[KlausST]

Hi,

In most cases only the input CMRR makes sense.
After the first stage often you don't have much CM fluctuation, thus no CMRR problem.

I recommend to focus on a dedicated circuit, because you can't expect us to give all answers for all possible circuits.

Klaus