Hi All,
Thanks for the reply. Let me clarify it.
First, since I am not trying to get the frequency response of the SC CMFB, the simulation done in Hspice is fine.
Secondly, an extra transistor is placed in parallel with the tail current source in both stage as the cmfb current control, this is not shown in the circuit diagram.
The problem is that I need to put a gain block in the SC CMFB circuit in order for the output voltages to converge to where I want the common mode output to be. This is because the CMFB loop gain for the second stage is very low.
So, my question is do I have to put a gain block in the SC CMFB circuit? If yes, how do you implement it? Or, is there any other simple ways to do it?
Thanks in advance.