An inverter circuit (60) includes an input section (62a-62d) configured to receive voltage from a voltage source (64) and to input the voltage to the circuit. A switching network (68,70) is connected to receive the input voltage from the input section. A controller (72) is placed in operational connection with the switching network (68,70) and is designed to control operation of the switching network. A resonant switching circuit (74,76) is configured to receive an output from the switching network (68,70). Load connections (80) are connected to the resonant switching circuit (74,76). A variable capacitance network (82,84,86) is connected to the load connection to provide a variable capacitance during circuit operation. A voltage in the capacitor (82) is clamped at predetermined levels. The clamping action acts to remove the capacitor (82) from the circuit or at least a portion of a cycle of operation of the circuit, wherein an effective variable circuit capacitance is obtained by operation of the clamping action. The circuit so obtained has a matching impedance with high Q-factor.