ABSTRACT
GaAs-based heterojunction bipolar transistor (GaAs HBT) power amplifiers (PAs) are widely used not only for GSM (Global System for Mobile Communications) handsets but also for CDMA (code division multiple access) handsets and wireless LAN/MAN (local area networks/metropolitan area networks) terminals [1-37]. The reason is that, compared to conventional GaAs FETs GaAs high electron mobility transistors (HEMTs), GaAs HBTs possess high power density with single voltage operation and excellent reproducibility leading to low cost and high yield. Without using fine process technologies, GaAs devices fabricated on the basis of bandgap engineering usually have the advantages of high frequency, high output power, high breakdown voltage, and high efficiency characteristics over fine process complementary metal-oxide-semiconductor (CMOS) ones. Moreover, GaAs standard processes offer substrate vias together with MIM capacitors and thick metal inductors fabricated on semi-insulating substrates with a resistivity of 1 MΩ cm or higher. The substrate vias make available common-emitter and common-source amplifier topologies without emitter or source bond wires, thereby helping realize high
17.1 Introduction ..................................................................................................485 17.2 Basics of GaAs-Based HBTs ........................................................................486
