transistors electronics

1. TRANSISTOR
Represented By:
Name : Manish Singh
Enrollment no: 20UEE103
Reg no : 2012488 ,Section -B

2. CONTENTS
1.Introductions
2.Terminal of Transistor
3.Principles of BJT
4.Configuration of Transistor
5.Different Modes Of Operation Of Transistor
6. Applications Of Transistor
• Transistor as Amplifier
• Transistor as a Switch

3. Introduction
Transistor: It is a solid state 3 terminal device whose output current ,voltage
and power are controlled by its input current.
BJT:- A Transistor is commonly known as Bipolar Junction Transistor (BJT)
because current conduction in it due to both types of charge carriers i.e
electrons and holes.
BJT is a 3 terminal ,2 junction device formed by sandwiching one of the
semiconductor material between 2 layers of other type.
Two types of transistor namely:-
a. NPN Transistor: It composed of two N-type semiconductor material
separated by a thin section of P type semiconductor material.
b. PNP Transistor: It composed of two P-type semiconductor material
separated by a thin section of N type semiconductor material.

4. Terminals Of Transistor
A transistor has 3 sections of doped semiconductor.
A section on one side is the emitter and the section on the opposite side is the
collector .The middle section is called the base and forms two junctions between
the emitter and collector.
Emitter :- It is heavily doped so that it can inject a large number of charge
carriers(electron in case of NPN and holes in case of PNP transistor)into the base.
Base :- It is lightly doped and very thin, so it passes most of the emitter injected
charge carrier to the collector.
Collector:- It is moderately doped and wider than base and emitter. It collects
charge carriers.

5. Principle of BJT
The emitter-base junction of BJT is forward-biased, whereas the collector-base junction is reverse biased.
The forward bias of the emitter-base junction causes the emitter current to flow and this emitter
current entirely flows in the collector circuit.
Working of NPN Transistor:- Working of PNP Transistor:-

6. Different Modes of Operation of Transistors
Depending upon the terminal which is used as a common terminal to the input and out
put terminals, the transistor can be connected in the following three configurations.
1.Common Base (CB) Configuration
2.Common Emitter (CE) Configuration
3.Common Collector (CC) Configuration

7. Different Modes of Operation of Transistors
There are mainly 3 possible ways of biasing a transistor . These are called modes of
operation in a transistor.
1.Active Region:- In this mode, the emitter base junction is forward biased while
the collector base junction is reverse biased.
In this region the transistor is used for amplification of signals.
In the active state, collector current is β times the base current, i.e.

8. Different Modes of Operation of Transistors
2.Saturation Region:-In this mode ,emitter- base junction as well collector base
junction both are forward biased.
In this case transistor is independent of base current. The collector and emitter curre
nts are maximum in this mode of operation.
The transistor has the effect of its collector and emitter being shorted. So, the
transistor acts like a close switch.

9. Different Modes of Operation of Transistors
3.Cutt-Off Region:-In this mode ,both the junction are reverse biased.
In this region, the transistor has practically zero current because the emitter does
not emit charge carriers to the base.
The transistor has the effect of its collector and base being opened and collector, emitt
er and base currents are all zero in this mode of operation.
Thus ,in this region , the transistor acts as an open switch.

10. Application Of Transistor
1.Transistor as a Amplifier:-To use transistor as an amplifier the weak signal to be amplified is applied
between emitter- base circuit and output is taken across the load resistor R(L),connected in the
collector circuit.
The low resistance in input circuit, lets any small change in input signal to result in an appreciable
change in the output. The emitter current caused by the input signal contributes the collector current,
which when flows through the load resistor RL, results in a large voltage drop across it.
Thus a small input voltage results in a large output voltage, which shows that the transistor works as an
amplifier.

11. Application Of Transistor
2.Transistor as a Switch:-A transistor can be used as a solid state switch. If the transistor is
operated in the saturation region then it acts as closed switch and when it is operated in the
cut off region then it behaves as an open switch.

12. THANK YOU