This resource provides engineers with a comprehensive treatment of silicon-germanium heterojunction bipolar transistors (SiGe HBT), a semi-conductor technology that is expected to revolutionise the communications industry by offering low-cost, high-speed solutions for emerging communications needs. It offers practitioners and students a from-the-ground-up understanding of SiGe HBT devices and technology from a very broad perspective. The text covers motivation, history, materials, fabrication, device physics, operational principles, and circuit-level properties associated with SiGe. This reference explains how to design, simulate, fabricate and measure a SiGe HBT, and offers an understanding of the optimization issues and design tradeoffs of SiGe HBTs and RF/microwave circuits built with this new technology.