FIELD EFFECT TRANSISTORS (FET)
A field-effect transistor (FET) is a semiconductor device in which the current flowing through a conduction channel i.e. between two terminals called the "Source" and the "Drain" and is controlled by an electric field arising from a voltage applied to another terminal, called the "Gate").
There are two classes of field-effect transistor:
1. The Junction-Gate Field-effect Transistor (JUGFET).
2. The Insulated-Gate Field-Effect Transistor (IGFET).
JUGFET: Has one (or more) semiconductor gate regions, which form P-N junction with the channel.
IGFET: Has an insulating layer (usually of oxide material) between the channel and the gate electrode (usually metal) It is often called the MOSFET (Metal Oxide semiconductor FET).
There is a furtyher subdivision of filed-effect transistors which isd due to the doping of the semiconductor:
1. An N-Channel field-effect transistor has an N-Type semiconducting channel.
2. A P-Channel field-effect transistor has a P-Type semiconducting channel.