Re: OP-AMP Problem
I am not sure about the circuit.But you can get think of that.
The circuit looks like a modulator.Like CW modulator(carrier wave modulator used in morse code generator)
The switch acts as message input.The vin is a carrier frequency.
The opamp acts as a low pass filter.The opamp works for low band carrier and will not allow any high frequency noise.
The two FETs are acting as an invetor and its output is connected through a capacitor so after pressing the switch, a pulse voltage goes out and it is captured in a big capacitor (in negative supply pin of opamp).
Please understand that i think so the circuit is, i am not sure.