Load-Pull Characterization and Modeling of Chip and Plastic Packaged HBT'S for PCS Amplifier Applications

Abstract

GaAs HBT’s are excellent candidates for PCS power amplifier applications which require a single low-voltage supply with good efficiency and linearity [l]. This paper describes the characterization and modeling of M/A-COM’s chip and plastic-packaged HBT for linear power amplifier applications at 1.88GHz. This analysis includes (1) a discussion of the device and package characteristics required for PCS amplifier applications (2) a complete load-pull characterization for power, efficiency, and linearity (3) a discussion of how these contours can be used to identify optimum matching conditions for linear amplifier design, and (4) the development and demonstration of a complete large-signal chip and packaged device model that accurately predicts the measured power, efficiency, and linearity. Through this analysis it is shown that for the GaAs HBT a significant improvement can be achieved in amplifier linearity by trading the device gain for linearity through an appropriate output termination.