I am reading "Intuitive IC Op Amps" by Frederiksen and getting stuck on one of the basic circuits. The book presents this image as a simple proxy for an op-amp.
Can someone help me understand a few things:
1) How is the Input biasing current and Output biasing current selected? What simple BJT circuits could realize these sources?
2) Why not replace Q3 with a diode?
3) What do D1 and D2 in the second stage do? Looks like they are trying to account for the diode drop of the Q6 and Q7 but I am not sure. What would happen if they weren't present? Why are 2 required?
4) What is Cc (compensation capacitor) doing? I vaguely understand that it's providing stability by pole separation. I can't get an intuitive grasp of what it's doing to the circuit, however.
5) Does anyone have a similar simplified image for a MOSFET implementation of a simple op-amp?