Bipolar Junction Transistor (BJT)


This is BJT , How it looks like

Construction of BJT(Bipolar junction Transistor)

Bipolar junction Transistor is a semiconductor device means it is made up of semiconductor materials i.e. silicon or germanium.

It has two types i.e. NPN and PNP

First we will discuss about NPN. In the NPN transistor, a P type semiconductor is sandwiched between two N type semiconductor.

In the above figure, a NPN transistor is shown. From the figure, you can see it has three terminals . The P terminal is called base and terminals attached to N type material is called emitter and collector.

Similar is the construction of PNP execept in PNP, one N type semiconductor material is sandwiched between two P type semiconductor material.

BJT symbol

As you have seen above, BJT has three parts.

1. Emitter: this is on the left side. It supply majority charge carries (holes or electrons) to the base. It is heavily doped.

2. Base: Middle part. It provides path to the charge carries and through the base, charge carries goes to the collector. It is very lightly doped and kept very thin.

3. Collector: Right part. Its work is to collect charge carries injected by emitter. It is moderately doped.


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