OVERLOAD DETECTING CIRCUIT FOR POWER AMPLIFIER

PURPOSE:To satisfy a detection function required for protecting operation and to accurately detect overload without being attected by the phase or the like of a power supply for load. CONSTITUTION:This overload detecting circuit is provided with a load current detecting part 30 for detecting the levels of load currents flowing into loads SPL, SPR and an output voltage detecting part 40 for detecting the output voltage of the output terminal of an amplifier and constituted so as to judge the existence of overload if the load current exceeds a prescribed current level only when the output voltage is less than a prescribed voltage level. When the output voltage exceeds a prescribed voltage level, the detection of a load current is invalidated. When output terminal voltage is more than a prescribed value, the absence of an abnormal state in the load such as the short-circuit of the output terminal is judged and the detection of an overcurrent is neglected, so that overload can be accurately detected without being attected by a phase or the like due to the reactance of the load. The output stage of an amplifier can be constituted of an amplifier element having a small rated current value margin.