Q. The current gain of a transistor in a common emitter configuration is 40. If the emitter current is 8.2 mA, then base current is
A) 0.02 mA
B) 0.2 mA
C) 2.0 mA
D) 0.4 mA
Explanation
(b) $\beta = \frac{I_{c}}{I_{b}} = \frac{I_{e} - I_{b}}{I_{b}} = \frac{I_{e}}{I_{b}} - 1\ \ or\ \ \ \frac{I_{e}}{I_{b}} = 1 + \beta$
or $I_{b} = \frac{I_{e}}{1 + \beta} = \frac{8.2}{1 + 40} = \frac{8.2}{41} = 0.20\ mA$.
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.