BJT working as a switch. (Photo credit: Wikipedia)

We received the Question “Please explain the working of a transistor as a switch” via email

The answers can be found from the following links.

http://www.electronics-tutorials.ws/transistor/tran_4.html

http://c8051.leongkj.net/learning_object/general_transistor_as_

switch.swf

If you have further doubts, please post them as comments

1. Explain the formation of energy Bands in solids. Distinguish between metals, insulators and semiconductors on the basis of band theory.
2. Distinguish between intrinsic and extrinsic semiconductors and the conduction in P type and N type semiconductors.
3. Explain the formation of depletion region and barrier potential in a pn junction.
4. Draw the circuit diagram used to study the Forward and reverse bias characteristics and draw the graph for forward bias and reverse bias.
5. Describe the working of a half wave rectifier  with the help of a neat labeled diagram and draw the input and output wave forms.
6. Describe the working of a full wave rectifier with the help of a neat labelled diagram and draw the input and output wave forms.
7. Draw the symbols of npn and pnp transistor. Show the biasing of a transistor and explain transistor action. 
8. Describe the working of an npn transistor in CE configuration as an amplifier.
9. Explain the working of a transistor in CE configuration as oscillator.
10. Explain the action of transistor as a switch.

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