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Transistor as a switch

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New Member
Hi guys,
I am new to electronics.I am doing my first yr of engineering in Electronics.Can somebody tell my how a Bipolar junction Transistor can be made to act as a switch.Waiting for ur reply.



New Member
Answer to your question..

Even I am a newbie to electronics but I have completed my fundamental course in Microelectronics and Digital Design.

Your question is "how to use transistor as a switch"

For this you need to know the following:

different regions of action by a transistor--active,cutoff,saturation.

MODES Collector-Base j'n Emitter-Base j'n

active region reverse biased forward biased
cut-off region reverse biased reverse biased
saturation reg. forward biased forward biased

The two extreme modes -saturation and cutoff, are very useful if the transistor is to used as switch.The BJT is usually made to operate alternatively in the cut-off and in saturation regions.
The concept of transistor as a switch is more stressed in the "digital design" rather than in your first course in electronics.So I suggest you thoroughly go through the charactersistcis of transistor in every region and how the transition takes place from each region to other.They are the most basic ones.

Good Luck

For reference :

N.N.Bhargava -- I dont remember the title but a very good book to learn your concepts.
Microelectronic Circuits--Sedra & Smith.
The best book is Millman and Halkias.-the Black Pad(popularly known)
--Electronic Devices.

For further queries you can contact me at :

[email protected]
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