internal circuit of op amp

[arava prakash]

hi friends
in general there are four stages in op amp
what are and why four stages are used?
what is thepurpose of using these stages
please reply me with circuit diagram of op amp using MOSFETs

 

[kam1787]

the four stages are stage 1, stage 2, stage 3, and stage 4
the purpose of stage 1 is for input, it is used because there is input
the purpose of stage 4 is for output,it is used because there is output

 

[ravindragudi]

I found this presentation useful in understanding the opamp internals. This may help you as well.

www.sonoma.edu/users/o/ouj/.../ES230_Spr_2012_Lecture_17.ppt

741 Op-Amp Circuit, Section 8.1 (Razavi) Chapter 12 (Sedra Smith)

 

[godfreyl]

Most (if not all) opamp circuits I've seen have three gain stages, not four.
There's a short explanation here.