SiGe, GaAs, and InP Heterojunction Bipolar Transistors

CHAPTER NINE

RF and Digital Circuits for Low-Voltage Applications

The drive toward HBT technology maturation has been motivated largely by the prospect of improving military electronic systems. The high f_T and f_max values, as well as other inherent device advantages, make the HBT ideal for front-end function from dc to microwave and millimeter-wave frequencies. The high transconductance values at low collector current make possible microwave amplifiers with very low power dissipation. The HBT’s high linearity, associated with its low output conductance, is attractive for low-harmonic-distortion applications such as a low-dc-power output-state amplifiers for use with HEMT low-noise input amplifiers. The high intrinsic gain (g_m/g_o) combined with high speed and freedom from trapping effects make HBTs ideal for wideband amplifiers. The exponential output current/input voltage relation combined with high-frequency performance and high substrate isolation make the HBT attractive for monolithic wide-dynamic-range logarithm IF amplifiers and analog multiplier-mixers. The low 1/f noise makes the HBT attractive for low-phase-noise oscillators. The high current density and high breakdown voltage are attractive for high-efficiency power amplifiers. For digital functions the HBT’s higher intrinsic f_max value, low base resistance, and lower substrate capacitance will permit higher speeds than Si bipolar transistors. Application-specific ICs (ASICs) that are fully customized will probably be ...