i wantto know the outp[ut when amplifier is operated in commom mode,,i tried so many times with different input but i got output voltage as 0 volt.can you suggest me the way i calculate cmrr value.
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the image i attached is the differential mode,,where output voltage is 0.1 microvolt..
With ideal identical devices in your simulation the CMRR for the difference signal will be essentially infinite, as you measured.
Note that your circuit is not a true differential stage since it does not have a common impedance in the emitter connections. You just have two single-ended stages being feed the same signal.