How Bipolar Junction Transistor Works?

The Bipolar junction transistor or BJT is constructed by three doped semiconductor regions. While studying BJT it is important to understand the basics of semiconductors and doping phenomenon first.

Semiconductor materials are bad conductors of current in their intrinsic state because they have limited number of electrons and holes in their valence shell. The doping process is used to increase the number of electrons and holes. In this process, different impurities are added so as to change the properties of materials.

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N-type and P-type semiconductors

When a pentavalent impurity item (the one having five electrons in valence shell) is added the resulting semiconductor is N-type. On the other hand, adding a P-type impurity results in P-type.
Now if an item is doped in such manner that one part is p-doped and other one is n-doped then it results in the formation of the pn junction. A BJT is made of three parts which are doped as either npn or pnp. In this video the complete illustration of its working along with its applications are presented.
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