question_answer

A common emitter amplifier circuit, built using an npn transistor, is shown in the figure. Its dc current gain is \[250,{{R}_{C}}=1k\Omega \]and \[{{V}_{CC}}=10V.\] What is the minimum base current for \[{{V}_{CE}}\] to reach saturation?  [JEE Main 8-4-2019 Afternoon]

A) \[100\mu A\]               

B) \[7\mu A\]

C) \[40\mu A\]     

D)   \[10\mu A\]

Correct Answer: C

Solution :

At saturation state, \[{{V}_{CE}}\]becomes zero \[\Rightarrow \]\[{{i}_{C}}=\frac{10V}{1000\Omega }=10mA\] now current gain factor \[\beta =\frac{{{i}_{C}}}{{{i}_{B}}}\] \[\Rightarrow \]\[{{i}_{B}}=\frac{10mA}{250}=40\mu A\]