Question

How does emitter resistor RE provide stability in CE short circuit gain obtained with hybrid pi model?

(a) Consumes less power

(b) Has an easier circuit design

(c) Automatically biases the circuit

(d) It does not provide stability

This question was posed to me in an online interview.

The question is from The CE Short Circuit Gain Obtained with the Hybrid PI Model in section High Frequency Transistor of Electronic Devices & Circuits

Answer 1

The correct answer is (c) Automatically biases the circuit

To elaborate: In a CE short circuit gain obtained with hybrid pi model, the emitter resistor provides stability by automatically biasing the circuit using negative feedback. The negative feedback negates any change due to the collector current with an opposing change provided by the base bias voltage and thus helps maintain circuit stability.