Question

Why is it essential to stabilize the operating point of a circuit?

(a) Thermal runaway, power efficiency, individual variations

(b) Temperature dependency of IB, individual variations, power efficiency

(c) Thermal runaway, Temperature dependency of IC, individual variations

(d) Temperature dependency of IC, thermal runaway, cost efficiency

The question was asked in a job interview.

Question is from The Alpha Cutoff Frequency in section High Frequency Transistor of Electronic Devices & Circuits

Answer 1

Correct answer is (c) Thermal runaway, Temperature dependency of IC, individual variations

Easiest explanation: It is essential to stabilize the operating point of a circuit to prevent thermal runaway, temperature dependency of IC and individual variations. Thermal runaway occurs because of the self – destruction of an unstable transistor. Temperature dependency on IC causes major variations in IE. Individual variations of parameters such as α and VBE cause huge fluctuations in IE.