CMFB and Operating Floating Amp

[ghostdog]

hi everybody,

when designing an amplifier like this one


and in Johan Huijsing, OPERATIONAL AMPLIFIERS, Theory and Design, Kluwer Academic Publishers, 2001, Ch 9 for this amplifier design says something like this


should i use a CMFB?

thk

 

[Fahmy]

I think the circuit already has a CMFB around the first stage as mentioned in the text. For the 2nd and 3rd stages they don't need CMFB because they are self-biased and not supplied by current sources from both top and bottom. This is assuming good matching of the current mirrors between the 2nd and 3rd stages.