a high - efficiency class d amplifier is described . in one embodiment , the amplifier contains two transistors which are turned on and off in sequence , the output being taken from the common node between the transistors . the efficiency of the amplifier is substantially increased by insuring that voltage across each of the transistors is substantially zero when it turns on . this advantage is achieved by connecting an inductance to the common node , so that the electrical energy stored in any stray capacitance is transferred to the inductance before any transistor is turned on .