Abstract: An amplifier with power supply switching is arranged so that the levels of the power supply voltages to be supplied to the amplifying elements of the output stage are switched over in accordance with the level and the rise time of a signal corresponding to an input signal of the amplifier, thereby, to enhance the power efficiency and to prevent an increase of distortion, as well as to reduce switching noises which tend to occur during the switching of the power supply voltages.

Abstract: A complementary push-pull amplifier comprising a pair of complementary transistors each of which is connected to a voltage source through a relatively large resistance and having the base biased with a voltage formed from the emitter-collector voltage of the transistor. Means for equalizing the amplitudes of second order distortion caused by the respective transistors is provided in a portion of the circuit other than the emitter circuit. The collector current is stabilized by the relatively large resistance connected to the collector and the asymmetry of the pair of transistors can be corrected by the amplitude equalizing means for cancellation of the second order distortion.