Sunday, 28 April 2013



A transistor is an electronic device that replaces the bulky and high power consuming electronic device.The transistor is the basic building block of electronics.Also it is reason for computers to be this much compact.

After the invention of the transistors only the monster size computers became compact and adaptable for human use.As the next stage of development transistors are combined together into a single chip called IC.Integrated Circuits (IC) are further advancements of transistors which are making computers more reliable.
The transistors are mainly of three types. They are                        
  • Bipolar Junction Transistor (BJT)
  • Field Effect Transistor (FET)
  • Unipolar Junction Transistor (UJT)


Bipolar means the conduction takes place by both majority and minority carriers.
And bipolar junction means it has two junctions.
It is a three terminal semiconductor device.
The terminals are Emitter, Base and Collector.
In BJT current is controlled by voltage.
BJT are popularly used in Computers, satellites, modern communication systems, etc.,

Field Effect Transistor (FET):

Field effect from the name itself we can understand that it involves the effect of electric field.
It is a unipolar device i.e., the current conduction takes place either by holes of electrons.
It is also a three terminal semiconductor device.
The terminals are Gate, Drain and Source.
In FET current is controlled by electric field.
FETs are commonly used in electronic watches, microprocessors, calculators, etc.

Unipolar Junction Transistor (UJT):

It has only one junction so it is called as unipolar junction.
It also has three terminals.
The terminals are Emitter, Base1 and Base2.
UJTs are commonly used in pulse transformers, saw tooth wave generator, blocking oscillators, etc.

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