Types of transistor

There are two types, they are:

NPN transistors

PNP transistors

Transistor consists of P type semiconductor and N-type; they are referred to as junction transistors.

They appear with a thin piece of semiconductor material maybe P or N type between a thick layer of either P or N type at each side depending on the semiconductor in the middle.If P type semiconductor is in the middle, N type semiconductor will be at both ends of the P type.

In this representation or system one of the outside layers is the emitter and the other is the collector. The middle layer is the base.