Abstract: A hot sensor detects a temperature of an output transistor and a cold sensor detects a temperature of a position distant from the output transistor. When the temperature of the hot sensor rises more than a reference temperature, a temperature detecting circuit asserts an overtemperature detecting signal, and when a temperature difference between the hot sensor and the cold sensor is more than a reference temperature difference, the above circuit asserts the temperature difference detecting signal. A current limiting circuit generates a limited current signal sequentially variable with the negative temperature characteristic for the temperature of the cold sensor and controls a drive current of the output transistor to a current value depending on the signal level of the limited current signal when the overtemperature detecting signal is asserted.