Why transistor is used as an amplifier?

Answer 1

A transistor acts like a valve or gate that opens and closes, and allows a current to flow. Since the amount of current that flows is controlled by another input, they can be used to make amplifiers. Carbon microphones and vacuum tubes have the same property, and so have also been used to make amplifiers historically.

Answer 2

A transistor doesn't have any mechanical parts to wear out, so it will last longer. A transistor can switch much faster than a mechanical device, so they can switch all the way from DC up into the microwave region. It is physically small. Very handy. It allows a relatively small controlling current to switch very large controlled currents.

Answer 3

Transistors are semiconductor devices that can be made very small as part of integrated circuits or can be individual devices. They can act as amplifiers and switches so they are useful in may applications in both digital and analog circuits. They come in many types suitable for different types of applications.

Answer 4

The question should be like: How can a transistor be used as an amplifier...??

Answer:

There are four mode of operations for a transisitor.

1. Forward active mode.

2. Reverse active mode.

3. Cut Off mode.

4. Saturation Mode.

To be an amplifier, transistor must be used in forward active mode.

To understand the modes, lets consider a pnp/npn transistor. In forward active mode, Emitter-Base Junction is forward biased & Collectror-Base Junction is reverse Biased.

In Reverse active mode, Emitter-Base Junction is reverse biased & Collector Base junction is forward biased.

In Cut off mode, both the junctions are reverse biased.

In Satuiration mode, both the junctions are forward biased.