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A switch-mode power amplifier topology that can achieve both a high conversion efficiency and low-output signal distortion is introduced. Such systems are desirable for ultra-high precision amplifiers that, for example, drive actuators in nanometre-accuracy mechatronic positioning applications in integrated semiconductor manufacturing. An efficient Class-D power stage, which is limited in output signal quality due to its inherent half-bridge interlock time, is combined through a magnetically coupled inductor with a dual buck conversion stage that does not require interlock time and, due to its circulating bias current that defines the half-bridge switching waveforms, achieves very low-harmonic output signal distortion. The control system can seamlessly adjust the current sharing of the two converter stages such that overall conversion efficiencies over 95% and output total harmonic distortion values below −100 dB are achievable at power levels up to several kilowatts. Detailed computer simulations demonstrate the feasibility of the concept.