C-band monolithic amplifiers using high-efficiency, refractory metal, multifunction-self-aligned-gate (MSAG) processing have been designed, fabricated, and tested. The class-B single-ended amplifier design uses reactive termination for higher order harmonics and achieves a power-added efficiency (PAE) of 70% with associated gain of 8 dB and output power of 1.7 W over the 5-6-GHz band. Power output, gain, and PAE are discussed as a function of input power, drain-source voltage, and gain-source voltage, and data on noise figure, AM-to-PM conversion, and second- and third-harmonic generation are included. The monolithic microwave integrated circuits (MMICs) exhibited excellent performance including -26 and -28 dBc second- and third-harmonic levels, respectively, at the maximum efficiency, clearly demonstrating the importance of careful harmonic termination. >