The thermal runway is not possible in FET because, as the tempera

The thermal runway is not possible in FET because, as the tempera
| The thermal runway is not possible in FET because, as the temperature of FET increases

A. The drain current increases

B. The mobility of charge carriers decreases

C. The mobility of charge carriers increases

D. The transconductance increases

Please scroll down to see the correct answer and solution guide.

Right Answer is: B

SOLUTION

Concept:

1) The thermal runway is not possible in FET because as the temperature of the FET increases, the mobility decreases, i.e. if the Temperature (T) ↑, the carries Mobility (μn or μ­p) ↓, and Ips↓

2) Since the current is decreasing with an increase in temperature, the power dissipation at the output terminal of a FET decreases or we can say that it’s minimum.

So, there will be no Question of thermal Runway at the output of the FET.

  • The thermal runaway takes place in a BJT.
  • Thermal Runway in BJT is a process of self-damage of BJT because of overheating at the collector junction due to an increase in Ic with Ico
  • If T↑, then Ico (Reverse separation current) ↑, which results in an increase in the collector current, i.e. Ic ↑.
  • Power dissipation at the collector junction increases in the form of heat which again raises the temperature and cycle continues.
  • If the above cycle becomes repetitive then the collector junction gets overheated and thereby thermal runway takes place.

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