[Help] Two stage fully differential opamp

[8k-rom]

I want design a two stages fully diff-opamp. But in many textbooks，each stage needs a cmfb circuit for balancing.

maybe there are some two stage fully diff-opamp just using only one cmfb~!!

who has any information about it ?

thanks in advance~!!

 

[batistuta]

you can check it out in allen's book...

 

[8k-rom]

you can check it out in allen's book...

In Allen's book ,for example,(fig7.3-12) the first stage doesn't utilize cmfb, but
I don't know whether it can work well


Anything wrong?

 

[MSSN]

I want design a two stages fully diff-opamp. But in many textbooks，each stage needs a cmfb circuit for balancing.

maybe there are some two stage fully diff-opamp just using only one cmfb~!!

who has any information about it ?

thanks in advance~!!

Yes, u can use a single CMFB for the two stage fully diff-opamp by sensing the common mode of the second stage and controlling the tail current source of the first stage

 

[williamy]

generally, the second stage doesnot need cmfb, or the outputs of the second are used the inputs of cmfb