ABSTRACT
InGaP/gallium arsenide (GaAs) heterojunction bipolar transistor (InGaP-HBT) power amplifiers (PAs) are widely used in global system for mobile communications and code division multiple access (CDMA) handsets and wireless local area network metropolitan area network terminals. This chapter introduces comprehensive design examples of a CDMA PA while focusing on the relationship between the distortion characteristics, bias circuits, and output matching conditions. It focuses on the emitter-follower-based bias circuit design. The chapter also describes the detailed relationship between the bias circuit, output matching, and AM-AM/AM-PM characteristics. Understanding the relationship is most useful for the actual design of linear PAs for use in CDMA and orthogonal frequency division multiplexing (OFDM) systems. According to the probability distribution function (PDF) of CDMA systems, the probability of a full output power state of a PA is much lower than that of a low output power state.
