A common emitter amplifier circuit, built using an npn transistor, is shown in the figure. Its dc current gain is 250, RC = 1kΩ and VCC = 10 V. What is the minimum base current for VCE to reach saturation ?

Question

A common emitter amplifier circuit, built using an npn transistor, is shown in the figure. Its dc current gain is 250, RC = 1kΩ and VCC = 10 V. What is the minimum base current for VCE to reach saturation ? (A) 100 μ A (B) 7 μ A (C) 40 μ A (D) 10 μ A

Tardigrade Admin · Accepted Answer

At saturation state, VCE becomes zero ⇒ iC = (10V/1000Ω) = 10 mA now current gain factor β = (iC/iB) ⇒ iB = (10mA/250) = 40 μ A

Q. A common emitter amplifier circuit, built using an npn transistor, is shown in the figure. Its dc current gain is $250, R_{C} = 1 k Ω$ and $V_{CC} = 10 V$ .
What is the minimum base current for $V_{CE}$ to reach saturation ?

$100 μ A$

$7 μ A$

$40 μ A$

$10 μ A$

At saturation state, $V_{CE}$ becomes zero
$\Rightarrow i_{C} = \frac{10 V}{1000Ω} = 10 m A$
now current gain factor $β = \frac{i _{C}}{i _{B}}$
$\Rightarrow i_{B} = \frac{10 m A}{250} = 40 μ A$

Q. A common emitter amplifier circuit, built using an npn transistor, is shown in the figure. Its dc current gain is 250,RC​=1kΩ and VCC​=10V. What is the minimum base current for VCE​ to reach saturation ?

100μA

7μA

40μA

10μA