Q87 / 120 · NEET 2012 (Mains) · Physics

The input resistance of a silicon transistor is $100 \Omega$. Base current is changed by $40 \mu \mathrm{A}$ which results in a change in collector current by $2 \mathrm{~mA}$. This transistor is used as a common-emitter amplifier with a load resistance of $4 \mathrm{k} \Omega$. The voltage gain of the amplifier is

  • Correct answer
    A
    2000
  • B
    3000
  • C
    4000
  • D
    1000

Solution

We know $$ V_g=\beta \frac{R_L}{R_i} $$ $$ =\frac{\Delta I_C}{\Delta I_B} \frac{R_L}{R_i} \quad\left(\because \beta=\frac{\Delta I_C}{\Delta I_B}\right) $$ On putting given values $$ \begin{aligned} & V_g=\frac{2 \times 10^{-3}}{40 \times 10^{-6}} \times \frac{4 \times 10^3}{100} \\ & V_g=2000 \end{aligned} $$

Hence, the correct answer is option: 'A'.

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