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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
Correct answer is option 'D'. Can you explain this answer?
Verified Answer
The total thermal resistance of a power transistor and heat sink is 20...
PD =(TJ-TA)/ H
=200-75/20=6.25W.
Now, IC = 6.25/4=1.56A.
=200-75/20=6.25W.
Now, IC = 6.25/4=1.56A.
Most Upvoted Answer
The total thermal resistance of a power transistor and heat sink is 20...
Understanding Thermal Resistance
The total thermal resistance (Rθ) of the power transistor and heat sink is given as 20°C/W. This value indicates how much the temperature of the junction (TJ) will rise per watt of power dissipated.
Calculating Maximum Power Dissipation
1. Maximum Junction Temperature (TJ)MAX: 200°C
2. Ambient Temperature (TA): 25°C
3. Temperature Rise (ΔT): TJ - TA = 200°C - 25°C = 175°C
Using the formula for power (P) dissipated:
P = ΔT / Rθ
P = 175°C / 20°C/W = 8.75 W
Finding Maximum Collector Current (IC)
The collector current (IC) can be calculated using the formula:
P = VCE * IC
Where VCE is the voltage across the collector-emitter junction.
Rearranging gives:
IC = P / VCE
IC = 8.75 W / 4 V = 2.19 A
This indicates the maximum collector current at an ambient temperature of 25°C.
Considering Increased Ambient Temperature
Now, if the ambient temperature rises to 75°C:
1. New Temperature Rise (ΔT): TJ - TA = 200°C - 75°C = 125°C
2. New Power Dissipation:
P = ΔT / Rθ
P = 125°C / 20°C/W = 6.25 W
Calculating New Collector Current (IC)
Using the same formula for the new conditions:
IC = P / VCE
IC = 6.25 W / 4 V = 1.56 A
Conclusion
Thus, the allowed value of collector current when the ambient temperature is 75°C is 1.56 A, confirming that the correct answer is option 'D'.
The total thermal resistance (Rθ) of the power transistor and heat sink is given as 20°C/W. This value indicates how much the temperature of the junction (TJ) will rise per watt of power dissipated.
Calculating Maximum Power Dissipation
1. Maximum Junction Temperature (TJ)MAX: 200°C
2. Ambient Temperature (TA): 25°C
3. Temperature Rise (ΔT): TJ - TA = 200°C - 25°C = 175°C
Using the formula for power (P) dissipated:
P = ΔT / Rθ
P = 175°C / 20°C/W = 8.75 W
Finding Maximum Collector Current (IC)
The collector current (IC) can be calculated using the formula:
P = VCE * IC
Where VCE is the voltage across the collector-emitter junction.
Rearranging gives:
IC = P / VCE
IC = 8.75 W / 4 V = 2.19 A
This indicates the maximum collector current at an ambient temperature of 25°C.
Considering Increased Ambient Temperature
Now, if the ambient temperature rises to 75°C:
1. New Temperature Rise (ΔT): TJ - TA = 200°C - 75°C = 125°C
2. New Power Dissipation:
P = ΔT / Rθ
P = 125°C / 20°C/W = 6.25 W
Calculating New Collector Current (IC)
Using the same formula for the new conditions:
IC = P / VCE
IC = 6.25 W / 4 V = 1.56 A
Conclusion
Thus, the allowed value of collector current when the ambient temperature is 75°C is 1.56 A, confirming that the correct answer is option 'D'.
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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)3.67Ab)7.56Ac)2.19Ad)1.56ACorrect answer is option 'D'. Can you explain this answer? for Electrical Engineering (EE) 2025 is part of Electrical Engineering (EE) preparation. The Question and answers have been prepared according to the Electrical Engineering (EE) exam syllabus. Information about 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)3.67Ab)7.56Ac)2.19Ad)1.56ACorrect answer is option 'D'. Can you explain this answer? covers all topics & solutions for Electrical Engineering (EE) 2025 Exam. Find important definitions, questions, meanings, examples, exercises and tests below for 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)3.67Ab)7.56Ac)2.19Ad)1.56ACorrect answer is option 'D'. Can you explain this answer?.
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