JEE Main & Advanced Physics Semiconducting Devices Question Bank Assertion and Reason

  • question_answer
    Assertion             :       A transistor amplifier in common emitter configuration has a low input impedence. Reason                 :       The base to emitter region is forward biased.  [AIIMS 2004]     

    A)             If both assertion and reason are true and the reason is the correct explanation of the assertion.

    B)             If both assertion and reason are true but reason is not the correct explanation of the assertion.

    C)             If assertion is true but reason is false.

    D)             If the assertion and reason both are false.

    E)             If assertion is false but reason is true.

    Correct Answer: A

    Solution :

                       Input impedance of common emitter configuration \[={{\left. \frac{\Delta {{V}_{BE}}}{\Delta {{i}_{B}}} \right|}_{{{V}_{CE}}=constant}}\] where \[\Delta {{V}_{BE}}=\]voltage across base and emitter (base emitter region is forward biased) \[\Delta {{i}_{B}}=\]base current which is order of few microampere. Thus input impedance of common emitter is low.


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