JEE Main & Advanced Physics Semiconducting Devices Question Bank Critical Thinking

  • question_answer
    A triode whose mutual conductance is 2.5 m A/volt and anode resistance is 20 kilo ohm, is used as an amplifier whose amplification is 10. The resistance connected in plate circuit will be           [MP PET 1989; RPMT 1998]

    A)            1 kW                                        

    B)            5 kW

    C)            10 kW                                      

    D)            20 kW

    Correct Answer: B

    Solution :

                       \[\mu ={{r}_{P}}\times {{g}_{m}}=20\times 2.5=50\] From \[A=\frac{\mu \,{{R}_{L}}}{{{r}_{P}}+{{R}_{L}}}\]Þ \[{{r}_{P}}+{{R}_{L}}=\frac{\mu \,{{R}_{L}}}{A}=\frac{50{{R}_{L}}}{10}=5{{R}_{L}}\]  Þ \[4{{R}_{L}}={{r}_{p}}\Rightarrow {{R}_{L}}=\frac{{{r}_{p}}}{4}=\frac{20}{4}=5k\Omega \]


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