Bipolar Junction Transistor and Its Benefits

The transistor is a semiconductor device, which can amplify the electronic signals, such as radio and television signal. It is an important ingredient of every electronic circuit. 

Transistor is a three terminal device, such as Base, Emitter, and Collector. It can be operating by three configurations, such as common base, common emitter, and common collector. According to the configuration mode it can be use for voltage as well as current amplification. The concept of transfer of resistance has given by the name of transfer resistor.

There are two types of transistors, such as unipolar junction transistor and bipolar junction transistor. In uni-polar transistor the current conduction is only due to one type of carriers, as majority carriers. The current conduction in bipolar transistor is because of both the types of charge carriers are holes and electrons. Therefore this is called bipolar junction transistor.

The bipolar junction transistor has two types, 

1. N-p-n type
2. P-n-p type

Principle of Bias Transistor:

To operate the transistor properly as an amplifier, it is necessary to bias correctly the two p-n junctions with external voltages. Depending upon the external bias voltage polarity usage and the transistor works in one three regions. 

1. Active region
2. Cut-off region
3. Saturation region

Construction of a transistor: 

The transistor can be constructing by use of the five basic techniques and accordingly they are classified as,
1. Grown type
2. Alloy type
3. Electro chemically etched type
4. Diffusion type

Grown Type: 

This technique is used to form the two p-n junctions of a grown-junction transistor. A single crystal is drawn from a melt of silicon or germanium whose impurity concentration is change during the crystal drawing operation.

Alloy Type: 

This type of construction is p-n-p transistor. Such construction is also known as fused construction. Here the center section is a thin wafer of n-type material. The collector is made larger than the emitter to withstand the heavy current and power dissipation at the collector base junction.

Electronically Etched Type:

In this technique, etching depression is made on opposite sides of the semiconductor wafer to reduce the thickness of the base region. The electro-chemically etching devices are also referring to the surface-barrier transistor. However these devices are no longer of commercial importance.

Diffusion Type:

Diffusion is a process, by which a heavy concentration of particles will diffuse into the surrounding region of lesser concentration. The primary difference between the diffusion and the alloy process is the fact that liquefaction is not reach in the diffusion process. Heat is applied to the diffusion process only to increase the activity of the elements can be involved.