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.