Hi ,

I came across one cmfb ckt and have a few quesitons, can someone pls gives some thoughts?

1. why is Vb involved in cmfb ckt?
2. if there is a reason for the existence of Vb here, based on charge conservation on topplate of c1(topone): Q=(Vcm-Vb)*c1=(Vop-Vcmfb)*(c1+c2), seems Vcmfb can be set by this eq. alone (without Von).  so am I missing anything or this ckt is flawed?

thanks,

Steve