A transconductance (using voltage to control current) electronic component used for switching and amplification. Acronym for Metal-Oxide-Semiconductor Field-Effect Transistor. (from http://en.wikipedia.org/wiki/Transistor)

A MOSFET is a three-terminal device which is used to control current flow in a circuit. The amount of current allowed to flow between drain and source is proportional to the voltage signal applied to the gate of the device. This is a major difference from a conventional bipolar junction transistor - the BJT collector-emitter current is controlled by base current, vs. the MOSFET drain-source current controlled by gate voltage.

The physical construction of a MOSFET creates a parasitic diode between drain and source, which must be taken into account when designing MOSFET circuits.

Major classifications of MOSFETS:

  • Enhancement mode or depletion mode
  • N-channel or P-channel

Depletion P-channel MOSFETs aren't used.

They are more used as switches than as amplifier.

Further reading: