ABSTRACT
In a radio frequency (RF) receiver, one of the most important features is its noise characteristics; that is, the attribute of collecting the desired input signal while producing less noise. The silicon-germanium (SiGe) heterojunction bipolar transistor (HBT) is a better contender for Silicon (Si)-based RF low-noise amplifiers (LNAs) because of its high speed, high gain, low noise, and good linearity characteristics. This chapter focuses on general design concerns and optimization strategies of LNAs. It demonstrates an example of an inductively degenerated cascode SiGe LNA optimization. When an LNA is designed exclusively as an RF building block, low voltage-standing-wave-ratio (VSWR) at the input and output of the LNA is also required. The chapter analyses a simplified device model which is used to derive analytical expressions and design rules of thumb. It summarizes the measured transistor parameters of a unit SiGe HBT. The chapter shows the large-signal nonlinear model of the SiGe HBT.
