Question

In a Darlington pair, the overall β=15000.β1=100. Calculate the collector current for Q2 given base current for Q1 is 20 μA.

(a) 300 mA

(b) 298 mA

(c) 2 mA

(d) 200mA

I got this question by my school principal while I was bunking the class.

I'd like to ask this question from Cascade and Darlington Amplifier in portion General and Feedback Amplifiers of Analog Circuits

Answer 1

The correct option is (b) 298 mA

For explanation: IB = 20 μA

IC = β.IB = 15000 x 20μ = 300 mA

IC1 = β1.IB = 100.20μ = 2mA

IC2 = 300 – 2 = 298mA.