The typical output characteristics curve for a transistor working in the common-emitter configuration is shown in the figure.
The estimated current gain from the figure is __________.

Solution

Physics sir · 3 steps

Read the jump in collector current between two curves and divide by the jump in base current.

1. What gain means. In common-emitter mode the current gain is β = (Δ I_C)/(Δ I_B) at a fixed V_(CE). Read it in the flat (active) region of the curves.
2. Read the figure. Each curve is 10 μA more in I_B than the one below it. Each step raises I_C by 2 mA, for example from 4 mA to 6 mA going from 20 μA to 30 μA.

   β = (Δ I_C)/(Δ I_B) = (2 × 10⁻³ A)/(10 × 10⁻⁶ A) = 200

3. So. The same ratio comes out for every pair of curves, and even (8 mA)/(40 μA) = 200. The current gain is 200.

The common slip: 0.2. Dividing 2 mA by 10 μA without converting units gives 0.2. Since 1 mA is 1000 μA, the gain is 200.

The idea to keep. For current gain from output characteristics, pick two curves, read Δ I_C in the flat region and divide by Δ I_B. Always bring mA and μA to amperes first.

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