I have a differential input Vin1 and Vin2 to PMOS P1 and P2. Vin2 is constact (1.5V) and have a capacitor (0.5pF) below transistor P2. ISS is 1uA and gm of Vin1 is about 5u. P2 is connected via switch and I want to control the gain by turning on the P2 for certain time. But I give time 1us gain is not as expected. I am taking the output in between P2 and capacitor. I expect gain to be (gm x time /C). What is wrong in my calculation.