In common emitter transistor amplifier, the output resistance is 500 k Ω and the current gain β = 50. If power gain of amplifier is 5 × 10⁶, what is the input resistance? (a) 325 Ω (b) 150 Ω (c) 350 Ω (d) 250 Ω

Answer: (d). Power gain = β² (Ro)/(Ri) 5 × 10⁶ = (50)² × (500 × 10³)/(Ri) Ri = (2500 × 5 × 10⁵)/(5 × 10⁶) = 250 Ω So the answer is (d) 250 Ω.

In common emitter transistor amplifier, the output resistance is 500… | MHT CET 2026 (11 Apr, Shift 1)

Q17MHT CET 2026 · 11 APR · SHIFT 1Medium

Junction Transistor

In common emitter transistor amplifier, the output resistance is $500$ k $\Omega$ and the current gain $\beta = 50$ . If power gain of amplifier is $5 \times 10^{6}$ , what is the input resistance?

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Answer: (d)

Power gain $= \beta^2 \dfrac{R_o}{R_i}$
$5 \times 10^6 = (50)^2 \times \dfrac{500 \times 10^3}{R_i}$
$R_i = \dfrac{2500 \times 5 \times 10^5}{5 \times 10^6} = 250\ \Omega$
So the answer is (d) $250\ \Omega$ .

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