Thermal Runaway MCQ’s

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This set of Electronic Devices & Circuits Multiple Choice Questions & Answers (MCQs) focuses on “Thermal Runaway”.

1. The thermal runway is avoided in a self bias because_________
a) of its independence on 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 on β

2. When the temperature is increased, what happens to the collector current after a feedback is given?
a) it remains same
b) it increases
c) it cannot be predicted
d) it decreases

3. Thermal runaway is_________
a) an uncontrolled positive feedback
b) a controlled positive feedback
c) an uncontrolled negative feedback
d) a controlled negative feedback

4. The thermal runway is avoided in a collector to base bias because_________
a) of its independence on β
b) of the positive feedback produced by the base resistor
c) of the negative feedback produced by the base resistor
d) of its dependence on β

5. Discrete transistors T1 and T2 having maximum collector current rating of 0.75A are connected in parallel as shown in the figure. This combination is treated as a single transistor to carry a single current of 1A, when biased with a self bias circuit. When the circuit is switched ON, T1 had draws 0.55A and T2 draws 0.45A. If the supply is kept ON continuously, it is very likely that_________

electronic-devices-circuits-questions-answers-thermal-runaway-q6

a) both T1 and T2 get damaged
b) both T1 and T2 will be safe
c) only T1 gets damaged
d) only T2 gets damaged

6. Which of the following are true?
a) TJ – TA = θPd
b) TJ – TA = θ/Pd
c) TJ – TA = θ+Pd
d) TJ – TA = θ-Pd

7. When the temperature is increased, what happens to the collector current after a feedback is given?
a) it remains same
b) it increases
c) it cannot be predicted
d) it decreases

8. When the collector current is increased in a transistor_________
a) the reverse current is increased
b) the temperature is increased
c) collisions of electrons decrease
d) the emitter does not emit electrons

9. When the power dissipation increases in a transistor, the thermal resistance_________
a) increases
b) cannot be predicted
c) decreases
d) remains same

10. Which of the following biasing techniques are prone to thermal runaway?
a) self bias
b) collector to base bias
c) fixed bias
d) the biasing technique is identified by temperature effect

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