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NEET Physics Semiconducting Devices NEET PYQ-Semiconducting Devices

  • question_answer
    The input resistance of a silicon transistor is \[100\,\Omega \]. Base current is changed by \[40\,\,\mu A\] which results in a change in collector current by 2 mA. This transistor is used as a common-emitter amplifier with a load resistance of \[4\,\,k\,\Omega \]. The voltage gain of the amplifier is                                                [AIPMT (M) 2012]

    A)  2000     

    B)  3000   

    C)  4000               

    D)       1000

    Correct Answer: A

    Solution :

    We know \[{{V}_{g}}=\beta \frac{{{R}_{L}}}{{{R}_{i}}}\]
    \[=\frac{\Delta {{I}_{C}}}{\Delta {{I}_{B}}}\frac{{{B}_{L}}}{{{R}_{i}}}\]      \[\left( \because \beta =\frac{\Delta {{I}_{C}}}{\Delta {{I}_{B}}} \right)\]
    On putting given values
    \[{{V}_{g}}=\frac{2\times {{10}^{-3}}}{40\times {{10}^{-6}}}\times \frac{4\times {{10}^{3}}}{100}\]
    \[{{V}_{g}}=2000\]


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