20. The LM317 has a maximum operating temperature of 125°C. The TO-220 case version shows a...
20. The LM317 has a maximum operating temperature of 125°C. The TO-220 case version shows a thermal resistance of 4 C°/W, junction to case. It also shows 50 C°/W, junction to ambient (no heat sink used). Assuming an ambient temperature of 50°C. What is the maximum allowable power dissipation for each setup? Assume that the first version uses a 15 C°/W heat sink with a 2 C°/W case to heat sink interconnection.
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Homework Answers
Maximum operating temperature =125⁰C
Version 1
Thermal resistance junction to case 
Thermal resistance case to heat sink 
Thermal resistance Heat sink to ambient 
Total thermal resistance from junction to ambient
Ambient temperature 
Maximum allowable power dissipation
Version 2
Thermal resistance junction to ambient without heat sink
Maximum allowable power dissipation 
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20. The LM317 has a maximum operating temperature of 125°C. The
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