Bipolar Junction Transistor

It works almost similar to a simple transistor. BJT is used for amplifying and switching purposes. It is a 3 terminal device (Base, Emitter, Collector) made of doped semiconductor material like silicon. The working of BJT includes both the electrons and holes. The electrons in base are called minority carriers plays a vital role in BJT for current flow) because the base is doped p-type which would make holes the majority carrier associated with only small part of current to flow) in the base.

BJT involves bi carrier types in charge flow that is both electrons and holes unlike the FET (Field effect Transistor) which has only one carrier type. It is of two types NPN AND PNP Transistors.

A BJT consists of three doped semiconductor regions, base region, the emitter region and the collector region as below.

These regions are respectively p type, n type and p type in a PNP, and n type, p type and n type in a NPN transistor as shown in the figures.

Each semiconductor region is connected to a terminal, labeled: emitter E, base B and collector C