help about fully differential gain boosting opa

[umount]

i wanna design a fully differential gain boosting opa, and also my additional stage is fully differential. i wonder is it necessary for my additional stage to have CMFB circuits and why they need or needn't? Thanks for your kindness

 

[PaloAlto]

It depends on what your additional stage is.

In general, you can say that if everything is fully differential, then the transistors can be in any OP. You would need the CMFB to set them to the rigth OP.