Microwave Power Amplifier Analysis and Design

Output power, efficiency, power dissipation, and optimum load-resistance expressions for idealized microwave Class A and B power amplifiers are derived based on a waveform analysis. The effects of device transconductance variation with bias and circuit harmonic termination are examined. Large-signal gain is determined by calculating the input power needed to produce a given output power. Both closed-form and CAD-based solutions are presented, all based on device dc I-V characteristics and small-signal models. A practical power amplifier design procedure is given and used to design a 22-GHz permeable-based transistor PBT power amplifier. Although the analysis and design results presented here are useful by themselves, they are also intended to be used in conjunction with other CAD and measurement techniques such as harmonic balance and load pull to arrive at a starting point. Device designers also should find these results useful, allowing them to predict how changes in device parameters will affect microwave power amplifier performance.