Thermal analysis of semiconductor devices-when do you need heat-sinks

Every electronics constructor and engineer knows that electronic devices like IC’s voltage regulators and CPU heat up. Temperature is a critical parameter for reliable system operation. System reliability is very closely related to devise temperature high or low. While temperature increases, the reliability drops exponentially. If you look in device datasheets, you will find a recommended Operating temperature range. For instance, the Voltage regulator 7805 can normally operate at 0 – 70°C temperature range when maximum Junction Temperature can reach 150°C. So how is the operating temperature range calculated? It is not as difficult as it may look like. We know that temperature is analogous to voltage, thermal resistance changed to electric resistance, power dissipation is as current, then:

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