What is transistor and it's classification?

Transistor is a very useful and common electronic component which is broadly used to amplify or switch electronic signal and power. It is a three terminal (Base, Emitter, Collector) semiconductor device. Depending on carriers and controlling system, the classification of transistor is given in the table below.

Classification Of Transistor

There is another type of transistor is called UJT which is not being used in these days.
The symbols of transistors ar given below

Depending on the syllabus and question pattern of Associate Program of IEB, I'll discuss mathematical problem solution of transistor.

NPN or PNP transistors are used in three basic configurations. These are:

1. Common Base configuration
2. Common Emitter configuration
3. Common Collector configuration Emitter Follower configuration

Equation of Current Gain alpha, beta gama and relation between them:

1. Common Base configuration: Current gain of common base configuration is denoted by α and α=Ic/Ie
2. Common Emitter configuration: Current gain of common emitter configuration is denoted by β and β=Ic/Ib
3. Common Base configuration: Current gain of common base configuration is denoted by γ and γ=Ie/Ib

Now, from transistor equation we have,
Ie = Ic + Ib
or, Ie/Ic = Ic/Ic + Ib/Ic [deviding by Ic]
or, 1/ α = 1 + 1/β
or, α = (β + 1)/β
or, β = α/(1 - α)

Again, Ie = Ic + Ib
or, Ie/Ib = Ic/Ib + Ib/Ib [deviding by Ib]
or, γ = β + 1
or, β = γ - 1


These equations will be used in future specially  β = Ic/Ib.

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