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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 VCE to reach saturation?

100µA

7µA

40µA

10µA

Solution:

Correct option is C. 40µA
At saturation state, VCE becomes zero ⇒ iC = 10V / 1000Ω = 10mA
now current gain factor β = iC / iB ⇒ iB = 10mA / 250 = 40µA