rail-to-rail folded cascode opamp

[govind_vlsi]

Hi ,

I am working on Folded cascode opamp .... I would like to know the differences between two-stage and folded cascode opamp .... Please suggest some good materials and books on folded-cascode opamps

Can any one help in this regard?

 

[naalald]

Hi,
In a telescopic cascode opamp you have a cascode architecture; that is if you have an NMOS common source first, you have an NMOS common gate after that in the signal path.
A folded cascode opamp is called to the stage that you have for example an NMOS common source and a PMOS common gate.
In these two cases there is just one high-impedance node in the circuit.
In a two stage opamp there are two high-impedance nodes in the circuit; that is you add a common source after the cascode (telescopic or folded) stage.
You can refer to Gray book or Razavi book for more information.

 

[zyyang]

Generally, the two stage opamp maybe need compensation, because it has two high-impedance nodes as naalald said, and the folded cascode opamp does not , may be the book <analog design essential> written by W.Sansen will be better for you to study

 

[qqic]

the first is one order while the second is 2 order

 

[govind_vlsi]

I have gone through the Analog Design Essentials by Sansen.... folded cascode amplifiers are well explained in that ..... Thanks