Before revision: As can be seen from the derating curve image for a hypothetical bipolar junction transistor, the device (rated for 100 W at ) cannot be expected to dissipate anything more than about 40 W if the ambient temperature is such that the temperature at which the device's case will stabilise (after heat-sinking) is .
After revision: As can be seen from the derating curve image for a hypothetical bipolar junction transistor, the device (rated for 100 W at ) cannot be expected to dissipate anything more than about 40 W if the ambient temperature is such that the temperature at which the device's case will stabilize (after heat-sinking) is .