ABSTRACT
Silicon-Germanium (SiGe) BiCMOS technology is making inroads in a wide variety of mixed-signal and high-performance circuit applications due to its attractive combination of excellent RF performance metrics at conservative lithographic feature size, together with the high integration levels and yield associated with standard silicon manufacturing. SiGe HBTs have been used in a variety of creative and unusual ways in circuit design, at times defying decades of conventional wisdom. Power gain and small-signal linearity measurements were performed on the saturated SiGe HBT operating in a common-emitter configuration and terminated with 50 Ω load and source impedances. There are some implications that need to be acknowledged before operating the HBT in weak-saturation. Only third-generation SiGe HBTs will yield useful performance when operated in weak-saturation. The RF signal at the output of the amplifying HBT will saturate due to gain compression even with small input RF powers.
