JEE Main 2022 · 28 July · evening · Single correct · +4 / −1
An n.p.n transistor with current gain β=100 in common emitter configuration is shown in figure. The output voltage of the amplifier will be
- (a) 0.1 V
- (b) 1.0 V
- (c) 10 V
- (d) 100 V
Answer and solution
Answer (b) 1.0 V
Solution
Physics sir · 3 steps
Voltage gain is current gain times the resistance ratio: β scaled by R_C/R_B.
- Read the circuit. The 1 mV signal drives the base through the 1 kΩ input resistance R_B. The output is taken across the 10 kΩ collector resistance R_C.
- Currents to voltages. The input signal sets i_B = vᵢₙ/R_B. The collector current is i_C = β i_B, and the output voltage is vₒᵤₜ = i_C R_C.
A_V = vₒᵤₜ/vᵢₙ = β R_C/R_B = 100 × (10 kΩ)/(1 kΩ) = 1000
- So. vₒᵤₜ = 1000 × 1 mV = 1 V, so the answer is (b).
The idea to keep. In a common emitter amplifier, voltage gain is β × R_C/R_B. The transistor multiplies current, and the resistor ratio turns that into a voltage gain.
Answer from the NTA final answer key. Solution by PrepWiser.