Abstract: A low level class D amplifier is disclosed. High effeciency is assured by operating the active devices in the switching or class D mode and recovering substantial portions of the power contained in the harmonics generated. The amplifier includes a switching circuit or class D active circuit, a harmonic impedance circuit and an RF circuit serially connected across a power supply for supplying DC power to the amplifier. During the conducting state of the class D active circuit, the harmonic impedance circuit limits the harmonic currents and stores energy as a magnetic field. Substantially all of the stored energy is recovered during the non-conducting portion of the active circuit and returned to the DC power supply. Limiting harmonic currents reduces the dissipation of the active devices. Recovering the stored energy substantially improves the efficiency of the amplifier.