In an experiment of CE configuration of n-p-n transistor, the transfer characteristics are observed as given in figure.
If the input resistance is 200 Ω and output resistance is 60 Ω, the voltage gain in this experiment will be ____________.

Solution

Physics sir · 3 steps

Read the current gain off the slope of the line, then scale it by the resistance ratio.

1. Current gain from graph. The transfer characteristic plots I_C against I_B, so its slope is β. Between the marked points, I_B rises by 100 μA while I_C rises by 5 mA.

   β = (Δ I_C)/(Δ I_B) = (5 × 10⁻³ A)/(100 × 10⁻⁶ A) = 50

2. Voltage gain. In CE mode, A_V = β × Rₒᵤₜ/Rᵢₙ. With the given values, A_V = 50 × 60/200 = 50 × 0.3.
3. So. The voltage gain is 15.

The common slip: 50. Stopping at the current gain β gives 50. You still have to multiply by Rₒᵤₜ/Rᵢₙ = 0.3 to get the voltage gain.

The idea to keep. The slope of the I_C versus I_B line is β. Voltage gain is β times output resistance over input resistance, so always convert mA and μA before dividing.

Answer from the NTA final answer key. Solution by PrepWiser.