JEE Main & Advanced Physics Semiconducting Devices Question Bank Critical Thinking

  • question_answer
    In NPN transistor, 1010 electrons enters in emitter region in 10?6 sec. If 2% electrons are lost in base region then collector current and current amplification factor (b) respectively are 

    A)            1.57 mA, 49                           

    B)            1.92 mA, 70

    C)            2 mA, 25                                 

    D)            2.25 mA, 100

    Correct Answer: A

    Solution :

                       \[{{I}_{e}}={{10}^{10}}\times 1.6\times {{10}^{-19}}\times \frac{1}{{{10}^{-6}}}=1.6\,mA\]    \[\left( \because I=\frac{Q}{t} \right)\] Since 2% electrons are absorbed by base, hence 98% electrons reaches the collector i.e. a = 0.98 Þ \[{{I}_{c}}=\alpha {{I}_{e}}=0.98\times 1.6=1.568\,mA\approx 1.57\,mA\] Also current amplification factor\[\beta =\frac{\alpha }{1-\alpha }=\frac{0.98}{0.02}=49\]


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