Transistors, Types and Advantages of BJT

Introduction

• Transistor is a three terminal device : Base, emitter and collector, can be operated in three configurations common base, common emitter and common collector.

• According to configuration it can be used for voltage as well as current amplification.

• The amplification in the transistor is achieved by passing input current signal from a region of low resistance to a region of high resistance. This concept of transfer of resistance has given the name TRANSfer-resISTOR (TRANSISTOR).

Types of Transistors

• There are two types of transistors : Unipolar junction transistor and bipolar junction transistor.

• In unipolar transistor, the current conduction is only due to one type of charge carriers, majority carriers.

• The current conduction in bipolar transistor is because of both the types of charge carriers, holes and electrons. Hence this is called Bipolar Junction Transistor, hereafter referred to as BJT.

• In BJT output current is controlled by input current and hence it is a current controlled device.

Types of BJT

1. n-p-n type 2. p-n-p type

Advantages of BJT

1. Low operating voltage

2. Higher efficiency

3. Small size and ruggedness and

4. Does not require any filament power

Review Questions

1. What is transistor ?

2. Explain the word transistor.

3. What are the types of transistors ?

4. What are the types of BJT ?

5. State the advantages of a transistor.