Question

What is the need for bootstrap biasing?

(a) To prevent a decrease in the gain of network

(b) To prevent an increase in the input resistance due to the biasing network

(c) To prevent a decrease in the input resistance due to the presence of multiple BJT amplifiers

(d) To prevent a decrease in the input resistance due to the biasing network

This question was addressed to me in class test.

My doubt stems from Cascade and Darlington Amplifier topic in section General and Feedback Amplifiers of Analog Circuits

Answer 1

Right answer is (b) To prevent an increase in the input resistance due to the biasing network

To explain I would say: A bootstrap biasing network is a special biasing circuit used in the Darlington amplifier to prevent the decrease in input resistance due to the biasing network being used. Capacitors and resistors are added to the circuit to prevent it from happening.