Characteristic of BJT in CB mode

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Purpose: -

To study and plot the BJT characteristics in a common base configuration.


Apparatus: -

BJT, ammeters, regulated power supply, breadboard, voltmeter, connection wires.


Theory: -

In his configuration, the base is made common to both the input and out. 

A BJT is a three-terminal two junction semiconductor device in which the conduction is due to both the charge carrier. Hence, it is a bipolar device. BJT is classified into two types NPN or PNP.

An NPN transistor consists of two N types in between which a layer of P is sand witched. The transistor consists of the three-terminal emitter, collector base. The emitter layer is the source of charge carrier and it is heavily doped with a moderate cross-sectional area.   The collector collects the charge carrier and hence moderate doping and large cross-section area. The base region acts as a path for the movement of the charge carrier. In order to reduce the recombination of holes and electrons the base region is lightly doped and is of low cross-sectional area.    

Current gain α: -

it is the ratio of the collector to base current at constant collector-base voltage. Its value ranges from 20-500

Procedure:-

Output characteristics: -

 it is the curve between collector current I

1)Connects the circuit as per the circuit diagram.

2)Set I

3)Plot the graph V

4)calculate α


Transfer characteristics:-

1)  set the V

2)  vary I

3)  note down I


Result:-

The transistor characteristics of CB configuration were plotted and obtained the value of α=___________                                   


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