FET

Field Effect Transistor

The FET consists of a semiconductor channel with electrodes at either end referred to as the drain and the source. A control electrode called the gate is placed in very close proximity to the channel so that its electric charge is able to affect the channel. The semiconductor channel where the current flow occurs may be either P-type or N-type. So there are two types or categories of FET known as P-Channel and N-Channel. FETs are also known as unipolar transistors as they involve single-carrier-type operation.

The field effect transistor is said to be the most like the triode vacuum tube. A vacuum tube has a cathode emitter which emits the electrons (negative terminal), and a collector plate which collects the electrons (positive terminal). The triode tube control grid will speed up or slow down electrons moving past it depending on polarity. Positive grid voltage will accelerate the electrons. The N type field effect transistor works the same way without the need for a heated filament.