Two stage op amp Vs folder cascode

[Emmett Seow]

Hi guys what are the advantages of the two stage op amp and disadvantages of it plz help me.

 

[viperpaki007]

Two stage opamps are normally used to enhance the gain of opamp as one stage can not provide high gain. However, there is a compromise, higher the number of stages, higher the number of parasitic poles, Therefore, it is more difficult to stabilize the opamp and to have wider unity gain bandwidth. Folded casocode single stage opamp may be broadband opamp compared to two stage opamps. Also in some case we need rail to rail input and output signals. Desiging a two stage opamp isolate the input from output to some extent and we can design the input and output stages seperately. i.e. input sigal swing limits are not dependent on output signal swing limits.