Thermal resistance dependency factors

Q.  On which factor/s do/does the value of thermal resistance depend?
- Published on 24 Sep 15

a. Size of transistor
b. Type of cooling system
c. Type of heat transfer mechanism
d. All of the above

ANSWER: All of the above
 

    Discussion

  • Sravanthi   -Posted on 25 Sep 15
    Thermal resistance (θ) is basically a proportionality constant term associated in specifying the relationship between the steady state temperature and the power dissipation at the junction. Hence, it is generally expressed in oC/W.
    The value of thermal resistance usually depends on the size of transistor, type of heat transfer mechanism (radiation, convection, conduction) 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 necessarily small so as to allow the smooth flow of heat from the junction of power transistor to the surrounding.

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