Question

The thermal runway is avoided in a self bias because_________

(a) of its independence of β

(b) of the positive feedback produced by the emitter resistor

(c) of the negative feedback produced by the emitter resistor

(d) of its dependence of β

The question was asked by my college director while I was bunking the class.

Query is from Self-Bias in section Transistor Biasing and Thermal Stabilization of Electronic Devices & Circuits

Answer 1

The correct answer is (c) of the negative feedback produced by the emitter resistor

The explanation is: The self destruction of a transistor due to increase temperature is called thermal run away. It is avoided by the negative feedback produced by the emitter resistor in a self bias. The IC which is responsible for the damage is reduced by decreased output signal.