A common emitter amplifier has a current gain 75. The collector resistance is 4 kΩ and the input resistance is 500 Ω. The voltage gain of amplifier is:
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → 600
In a common emitter amplifier the voltage gain is the current gain multiplied by the ratio of the output (collector) resistance to the input resistance.
\( \displaystyle A_V = \beta\,\frac{R_C}{R_{\mathrm{in}}} \)
\( \displaystyle A_V = 75\times\frac{4000\,\Omega}{500\,\Omega} = 75\times8 = 600 \)
Note: This question is from the pre-rationalised NCERT book (2022-23). The topic was removed from the latest NCERT book (2026-27), and it also appears to be out of the CUET 2026 syllabus.
NCERT (Pre-rationalised edition, 2022-23):
Transistor as a Device – “… We can express the voltage gain AV in terms of the resistors in the circuit and the current gain of the transistor as follows. … So, the voltage gain of this CE amplifier (Fig. 14.32) is given by
\( \displaystyle A_V = -\beta_{ac}\left(R_C / R_B\right) \qquad (14.14) \)”