transistor

A semiconductor device with three terminals composed of two or more PN junctions. It is an active device that allows control of the collector current or gate voltage through the base current or drain current, and is often used as an amplifier circuit. Types include bipolar transistors, which have the function of amplifying current, and field-effect transistors (FETs), which have the function of amplifying voltage. They are also widely used in switching power supply circuits.