Question

On which factor/s do/does the values of thermal resistance depend?

(a) Size of transistor

(b) Type of cooling system

(c) Transistor size & cooling system type

(d) Number of holes

I got this question in an online interview.

My query is from Thermistor and Sensistor Compensation topic in division Transistor Biasing and Thermal Stabilization of Electronic Devices & Circuits

Answer 1

The correct option is (c) Transistor size & cooling system type

For explanation: The value of thermal resistance usually depends on the size of transistor, type of heat transfer mechanism and the type of cooling systems (natural cooling, forced air cooling, etc). It also depends on the thermal connectivity of device to a heat sink or metal chassis. Thermal resistance of a power transistor is always less than that of logic level transistor. The value of thermal resistance should be essentially small so as to allow the smooth flow of heat from the junction of the power transistor to the surrounding.