A low voltage, switch mode PHEMT power amplifier with a 0.1 μm gate length and a low loss, lumped element, output matching circuit is disclosed that provides high performance over a frequency range of 1.4 GHz-2.5 GHz. The amplifier makes use of monolithic circuit technology for the first stage and output transistor, and uses a printed circuit board with surface mount components for the output matching network. The power output of the power amplifier is stable over a range of 60 degrees centigrade, has high power efficiencies of 44-53% with greater than 2 watts output power over the frequency range of 1.4 GHz and 2.5 GHz. In addition, through drain voltage control, the output power can be varied over a wide range between about 0.8 to 2.5 watts while still maintaining a high efficiency in the range of 50±3%.