hi!
i'll do my best! first your differential pair turns on if vin is correct. which will simultaneously turn on M9 and M10. given the right vds for m1 and m2, m3 and m4 will turn on, so and so forth until all transistors are on. from the 200 uA current source, the current will split into 100 uA each per leg (ideally). you are forcing 100 uA to pass through m1 for example. it is basically two pairs of pmos cascoded (m3 m4 and m9 m10) with nmos pairs (m1 m2 and m11 m12). the common source stage is an inverting amplifier. it is usually needed for very high gain. you need a very high gain for your amp to swing (voltage gain versus input voltage) from 0 to say up to 5 V (vdd). Cc is a compensting capacitor. since very high gain op amps have relatively small bandwdith, you need a compensating capacitor to increase its bandwidth effectively.
- al