Question

what are the applications of FET

Answer 1

The main reason one uses a FET, Field Effect Transistor, is it's very high input impedance even though it has less BW, Band Width, than a BJT, Bipolar Junction Transistor. Generally their used together using the FET to give high input impedance followed by gain circuitry using BJT's. They are also used in many, if not all, digital circuitries.