What Is a Field Effect Transistor? FET Types, Working Principle, Applications, and Selection Guide

A Field Effect Transistor, commonly called a FET, is a voltage-controlled semiconductor device that uses an electric field to control current flow between two terminals called the source and drain. Unlike bipolar junction transistors, which require input current at the base, FETs are controlled mainly by voltage at the gate terminal. This gives FETs high input impedance, low control power, and strong advantages in switching, amplification, power management, RF circuits, sensor interfaces, and modern integrated circuits.