A 20-GHz low-noise amplifier with active balun in a 0.25-μm SiGe BICMOS technology

A 20-GHz low-noise amplifier (LNA) with an active balun fabricated in a 0.25-μm SiGe BICMOS (f_t=47 GHz) technology was presented by the authors in 2004. The LNA achieves close to 7 dB of gain and a noise figure of 4.9 dB with all ports simultaneously matched to 50 Ω with better than -16 dB of return loss. The amplifier is highly linear with an IP_1dB of 0 dBm and IIP₃ of 9 dBm, while consuming 14 mA of quiescent current from a 3.3-V rail, with temperature-compensated biasing. To the authors´ knowledge, the LNA delivers the lowest reported noise figure and highest linearity for a silicon implementation of a combined active balun and LNA at 20 GHz, and is the first implementation of an active balun with an LC degenerated emitter-coupled pair. Here we expand on that work, with an analysis of the balun operation and noise optimization of the design.