Direction for: In each of the following questions a statement of Assertion is given followed by a corresponding statement of Reason just below it. Of the statements mark the correct answer as
Assertion: A transistor amplifier in common emitter configuration has low input impedance. Reason: The base to emitter region is forward biased.A) If both assertion and reason are true and reason is the correct explanation of assertion
B) If both assertion and reason are true but reason is not the correct explanation of assertion
C) If assertion is true but reason is false
D) If both assertion and reason are false
Correct Answer: B
Solution :
Input impedance of common emtter configuration is given by \[=\left( \frac{{{\Delta }_{BE}}}{\Delta {{I}_{B}}} \right){{V}_{CE}}=\operatorname{constant}\] Here, \[{{\Delta }_{BE}}=\] voltage across base and emitter \[\Delta {{I}_{B}}=\] base current of the order of few microampere. Hence, impedance of common emitter is low. In a transistor, emitter-base region should be forward biased for good amplification.
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