Dear friends,
Thank you all for your nice contribution to my post,
Let me say that you all are agree that I must go to measure the common mode gain and the differential gain.
There is one point might I did't make it clear for you, I don't mean by the closed system is that I have an op-amp connected in feedback,
But what I wanted to say that I need to test the CMRR in such a way similar to the method you learned me, you remember in my former post when I was simulating the AC char of the opamp then you suggested me to simulate in closed loop with diffstbprobe and STB analyses,
The closed loop is just a thing I want to add to my simulation to make it stable independent of the offset voltage (VOS), and why I need it independent of the (VOS) is because that I want to simulate the CMRR over the entire range of the ICMR, so if the VOS is changing when I change the ICMR, then the measurement of the CMRR will fail.
- - - Updated - - -
According to your explanation I have found this configuration from analog devices, please see it below
is it what you suggested right ?
I also plotted the configuration based on it but for my fully differential amplifier to refer to it please in your kind talk