CBSE Class 12 · 2009 · SemiconductorsLong Answer

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(i) Draw a circuit diagram to study the input and output characteristics of an n-p-n transistor in its common emitter configuration, and draw the typical input and output characteristics.
(ii) Explain, with the help of a circuit diagram, the working of an n-p-n transistor as a common emitter amplifier.

Solution

(i) Connect the n-p-n transistor in CE configuration with

V_{B B}

biasing the base (through a resistor) and

V_{C C}

biasing the collector through

R_{C}

, with meters for

I_{B}

V_{B E}

I_{C}

V_{C E}

.
Input characteristic:

I_{B}

versus

V_{B E}

at fixed

V_{C E}

. Output characteristic:

I_{C}

versus

V_{C E}

for several fixed

I_{B}

.
(ii) Amplifier: the base-emitter junction is forward biased and the collector-emitter output reverse biased through

R_{C}

; the ac signal is applied to the base.
The signal changes the base current, which produces a

β

-times larger change in collector current; the varying drop across

R_{C}

is the amplified output,

18 0^{\circ}

out of phase with the input.

A_{V} = β \frac{R _{C}}{R _{B}} .

A_{V} = β \frac{R _{C}}{R _{B}} .

CBSE Class 12 Board · 2009 · Subjective

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CBSE Class 12 · 2009 · SemiconductorsLong Answer

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