InP-based complementary HBT amplifiers for use in communication systems

Abstract

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 h fe>30, BV ECO=5.6 V, and f T and f max 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.