Q79 / 90 · JEE Main 2017 (09 Apr Online) · Physics

The current gain of a common emitter amplifier is $69$ . If the emitter current is $7.0 mA$ , collector current is :

A
$69 mA$
B
$0.69 mA$
Correct answer
C
$6.9 mA$
D
$9.6 mA$

Solution

β = 69 = \frac{I_{C}}{I_{B}}

α = \frac{β}{1 + β} = \frac{69}{70} = \frac{I_{C}}{I_{E}}

I_{C} = I_{E} \times \frac{69}{70}

I_{C} = \frac{69}{70} \times 7

I_{C} = 6.9 mA

.

Hence, the correct answer is option: 'C'.

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