Question

The total thermal resistance of a power transistor and heat sink is 20°C/W. The ambient temperature is 25°C and (TJ)MAX=200°C. If VCE=4V, find the maximum collector current that the transistor can carry without destruction. What will be the allowed value of collector current if ambient temperature rises to 75°C?

(a) 3.67A

(b) 7.56A

(c) 2.19A

(d) 1.56A

The question was asked in semester exam.

The above asked question is from Thermal Stability topic in division Transistor Biasing and Thermal Stabilization of Electronic Devices & Circuits

Answer 1

The correct option is (d) 1.56A

To elaborate: PD =(TJ-TA)/ H

=200-75/20=6.25W.

Now, IC = 6.25/4=1.56A.