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

 

[erikl]

Fully differential opAmps always need a CMFB. Here, the CMFB stage is already integrated: M41 - M46 . The common mode feedback works from M46 into M36 , whereas M43 to M34 as well as M44 to M33 provide positive 1/N feedback to the output stage.

 

[ghostdog]

thanks erikl