Help me to understanding this

[maori]

im newbiee and still not quite understand about this flow of rail to rail op amp.
here im attach my circuit study.this actually a get from internet.but i want to know the opamp operation in detail

1)can anyone explain to me the flow..for each transistor when it will be operate.i really need to know in detail

2)can anyone explain to me especially M12,M8,M5,M7and M4

please I quite stuck here.

3)is there any reference that show the flow that almost same as this circuit

 

[zizu]

Pls check sec 9.7 in Razavi and u will get some idea with the complementary input stage in this opamp.

 

[garfieldarcy]

it is current control of input stage
Ron Hogervorst's papers about rail to rail may help

 

[hardings]

Something wrong in your circuit, the 1st input stage?

 

[niezimei]

there is an error in your input stage connection.This is a rail-to-rail input current mirror OTA with buffer stage to drive large cap load.