Question

The current gain of a transistor in common emitter configuration is 45. If the resistances in collector and base sides of the circuit are 4.5 kΩ and 900 Ω, the voltage gain of the amplifier is:

• A. 90
• B. 150
• C. 225
• D. 135

Hint:

The voltage gain in a common emitter amplifier depends on both the current gain and the ratio of the collector and base resistances. In this case, the high current gain of 45 results in a large voltage gain.

Answer 1

The Correct Option is C

In a common emitter amplifier, the voltage gain (\(A_v\)) is given by: \[ A_v = \text{Current Gain} \times \frac{R_C}{R_B} \] Where: - Current gain = 45
- \(R_C = 4.5 \, \text{k}\Omega\) (collector resistance)
- \(R_B = 900 \, \Omega\) (base resistance)
Now, substituting the values: \[ A_v = 45 \times \frac{4.5 \times 10^3}{900} \] \[ A_v = 45 \times 5 = 225 \] Thus, the voltage gain of the amplifier is 225.