InP-based Complementary HBT Amplifiers for use in Communication Systems

This paper addresses a method to improve the linearity characteristics of power amplifiers by developing a PNP HBT technology and combining the PNP HBTs with NPN HBTs in a push-pull amplifier. InP-based PNP HBTs were fabricated with hfe > 30, BVECO = 5.6 , and fT and fmax of 11 and 31 GHz, respectively, which is the best reported for InAlAs/InGaAs PNP HBTs. Common-collector push-pull amplifiers were simulated using these HBTs, demonstrating an improvement of 14 dB in second harmonic content under Class B operation. A common-emitter push-pull amplifier fabricated with the same HBTs demonstrated the best IM3 (by ~7 dBc) and smaller second harmonic content (by ~9 dBc) compared with NPN HBTs. In addition, the circuit produced 1.32 dBm more output power than the NPN HBT alone at 1 dB of gain compression. This work was supported by ARO MURI under Contract DAAH04-96-1-0001.