I am designing a two stage differntial opamp. I am not sure if i have to design two CMFB or just use one for both. Im not really sure what the difference is. Does anybody know?
Hi,
Generally speaking, one CMFB is enough for the whole opamp, you can detect the output common mode voltage, which is compared with a reference, then the output is feedback to the first stage of the opamp.
It depends on your circuit. If the gain of both two stages is very high, you need two CMFB. If one stage's gain is very low(<0.5), you don't need CMFB in this stage.
It depends on whether one CMFB can do the trick.
If it can't, then you need to use 2 CMFB.
You can run some simulation & check op poits to help you decide.
I am designing a two stage differntial opamp. I am not sure if i have to design two CMFB or just use one for both. Im not really sure what the difference is. Does anybody know?