Analog electronics Experiment 6 aim to study the input and output characteristics of a transistor in common emitter configuration

 Note remember page numbers

Aim: To study input and output characteristics of a transistor in its various configurations (CE

and CB).

Apparatus:

Bread board, Variable and fixed D.C sources, variable small signal A.C. source, resistances,

multimeters, BJT, connecting wires.

OR

Transistor Characteristics trainer kit with connecting leads and power supply.

Theory: Transistor is a semiconductor device consisting of two p-n junctions. It has three

terminals, to handle I/P and O/P four terminals are needed. Therefore, one terminal is made

common. A transistor can be connected in three Ways CB, CE, and CC.

Common base : Base is made common. I/P is connected between base & emitter and O/P is taken

between base & collector.

1) Input characteristics: The curve plotted between emitter current IE & the emitter-base voltage

VBE constant collector-base voltage VCB.

2) Output characteristics: The curve plotted between collector current IC & collector-base

voltage VCB constant emitter current IE.

Common Emitter: In common Emitter configuration input is applied between base and emitter

while the output is taken across emitter and collector. Thus the emitter forms the terminal

common to doth input and output circuits. The load resistance is connected at collector.

(1) Input characteristics: The curve plotted between base current IB & the emitter-base voltage

VBE constant collector-emitter voltage VCE

(2) Output characteristics: The curve plotted between collector current IC & collector-emitter

voltage VCE constant base current IB. 

Procedure:

CB Configuration:

 Connect the circuit as per the circuit diagram.

Input characteristics:

(a) Make the connection as per circuit diagram.

(b) Switch ‘ON’ the supply & set V = 0V

(c) Vary V in step & note down the emitter current I at each step .

(d) Set V = 1V & again repeat the same procedure .

(e) Draw the graph.

Output characteristics:

(a) Make the connection as per circuit diagram.

(b) Set the value of I = 1mA

(c) Vary V in step & note down the collector current I at each step.

(d) Set I = 2mA & repeat the same procedur

(e) Draw the graph.

CE Configuration:

 Connect the circuit as per the circuit diagram.

Input characteristics:

a) Keep emitter - collector voltage constant.

b) Vary emitter-base voltage in steps and note down base current reading.

c) Readings are tabulated and graph is drawn.

Output characteristics:

a) Keep base current constant.

b) Vary collector-emitter voltage in steps and note down emitter current.

c) Readings are tabulated and graph is drawn.

Conclusion: The input and output characteristics of transistor in CB and CE configuration has

been plotted. With the help of output characteristics we can also calculate ac & dc current gain in

CB and CE configuration.

Precautions:

(1) Always connect the voltmeter in parallel & ammeter in series as shown in fig.

(2) Connection should be proper & tight.

(3) Switch ‘ON’ the supply after completing the ckt.

(4) DC supply should be increased slowly in steps

(5) Reading of voltmeter & Ammeter should be accurate.