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A transistor is connected in common emitter mode. In the collector circuit the voltage drop across the resistor of $800 \; \Omega$ is $0.5 V$ . If current gain $\alpha$ is $0.96$ What is base current

$(a)\;30\;\mu A \\ (b)\;20\;\mu A \\ (c)\;24\;\mu\;A \\ (d)\;26\;\mu\;A $

1 Answer

Collector current $IC=\large\frac{V}{R}$
$\qquad= \large\frac{0.5}{800}$$A$
Also $\beta=\large\frac{\alpha}{1- \alpha}$
$\qquad= \large\frac{0.96}{1-0.96}$
$\qquad= 24$
and $\beta =\large\frac{I_c}{I_b}$
$\therefore I_b=\large\frac{I_c}{B}$
$I_b =\large\frac{0.5}{800 \times 24}$
$\qquad= 26\;\mu A$
Hence d is the correct answer.
answered Jan 31, 2014 by meena.p

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