Monolithic microwave GaAs power FET amplifier

Design considerations for monolithic microwave GaAs FET power amplifiers are discussed. Attention is given to circuit topologies for the impedance matching of microstrip transmission lines, inductors, and capacitors, RF grounding techniques and the effects of substrate thickness on thermal resistance. Characterization procedures for monolithic power amplifier circuits are also discussed, including the power-gain evaluation and impedance measurement of discrete FETs and input/output matching circuits by external broadband matching networks and measurements of light emission to determine interstage matching. Examples of practical single-ended, push-pull and paraphase monolithic GaAs power amplifier circuits are presented, and results of external circuit modifications to allow operation at frequency bands other than those intended are indicated. It is concluded that as monolithic processing technology matures, improved amplifier performances in the areas of output power, gain, bandwidth, efficiency and frequency limits are expected, and important microwave system applications will develop.