These are semiconductor devices that have three leads and can be used as amplifiers or switches. A small current on one lead can control a bigger current flowing through the other two leads. There are two types of transistors: Bi-polar and field effect.
Bipolar Transistors
If you add a second juncton to a PN junction diode, a 3-layer silicon sandwich will be created. It can either be NPN or PNP and in both cases the middle layer behaves as the gate that controls the current moving through the three layers. The three layers are known as the emitter, base and collector.
Field Effect Transistors
These transistors are known as FET’s and have become more important than bipolar transistors because they are easier to make and require less silicon. Field Effect Transistors are divided into Junction and Metal Oxide Semiconductor. In both types, output current is controlled by a small input voltage and a very minute input current and are very fast.
Related posts: