High Efficiency Switch-Mode Power Amplifier

A switch mode power amplifier includes a transistor responsive to input signals above 1.0 GHz and which includes one terminal coupled to ground and another terminal conductively coupled to a power source. A resonant circuit coupled the second terminal to an output with a resistive load coupled across the output and ground. When the transistor is turned on the second terminal is coupled to ground and when the transistor is turned off, current from the power supply to the second terminal is steered into internal capacitance of the transistor and causes voltage on the second terminal to rise to a maximum value and then decrease, the voltage at the second terminal being coupled to the output terminal through the resonant circuit.; In preferred embodiments, the transistor comprises a compound semiconductor field effect transistor with the first terminal being a source terminal and the second terminal being a drain terminal. The field effect transistor is preferably a compound high electron mobility transistor (HEMT) or compound MESFET, but in other embodiments the transistor can be the compound LDMOS, compound bipolar transistor, or compound MOSFET.