The GATE Grind

GATE 2021 IN – Question 25

Analog Electronics · Diodes and transistor circuits · 1 mark · Numerical answer

Transistors $Q_1,Q_2$ have current gains $\beta_1=99$, $\beta_2=49$, respectively. For the shown circuit, current $I_{B2}$ is ______ μA.

Diagram for GATE 2021 IN question 25

Practise this question in The GATE Grind →

Show answer and explanation

Correct answer: 10 to 10

Explanation

For Q1, IE1=(β1+1)IB1=100IB1=50 mA, giving IB1=0.5 mA. This is Q2’s emitter current, IE2=(β2+1)IB2=50IB2.

Therefore IB2=0.5/50 mA=**10 μA**. Use β+1 because the indicated currents are emitter currents.