Transistor

Transistor

• A transistor is a semiconductor device used to amplify or switch electronic signals and electrical power. 
• c.f., switch
• can be either in an "on" or "off" state
• It is composed of semiconductor material usually with at least three terminals for connection to an external circuit. 
• A voltage or current applied to one pair of the transistor's terminals controls the current through another pair of terminals. 
• Because the controlled (output) power can be higher than the controlling (input) power, a transistor can amplify a signal.