# The collector and emitter current levels for a transistor with common base dc current gain of 0.99 and base current of 20 μA are respectively

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The collector and emitter current levels for a transistor with common base dc current gain of 0.99 and base current of 20 μA are respectively
1. 2 mA and 1.98 mA
2. 1.98 μA and 2 mA
3. 1.98 mA and 2 mA
4. 2 mA and 1.98 μA

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Correct Answer - Option 3 : 1.98 mA and 2 mA

Concept:

Collector current can be calculated as:

Ic = βIb ----(1)

where β is common emitter DC gain and

$β=\frac{\alpha}{1-\alpha}$ -----(2)

Emitter current can be calculated by:

Ie = Ib + Ic -----(3)

Calculation:

Given:

α = 0.99

Ib = 20 μA

From equation (1) and (2),

Ic can be calculated:

$\beta=\frac{0.99}{1-0.99}=99$

Ic = 99 × 20

Ic = 1.98 mA

From equation (3)

Ie can be calculated as:

Ie = 1.98 + 0.02 = 2 mA.