Analysis and design of an ultra-wideband low-noise amplifier using resistive feedback in SiGe HBT technology

We present the analysis and design of an inductorless wide-band SiGe heterojunction bipolar transistor low-noise amplifier (LNA) using a resistive feedback scheme for application in ultra-wideband systems. Multiple feedback loops enable sufficient gain and low noise figure, and is competitive with conventional narrow-band cascode LNAs using an emitter degeneration inductor. Measurement results show 20-dB gain with 1-dB variation over 3-10 GHz, and a matched input and output with less than -10-dB reflection. The minimum noise figure is 3.05 dB at 3 GHz and increases to 4.5 dB at 10 GHz. For the analysis and design of such wide-band amplifiers, analytical expressions describing the basic performance tradeoffs are derived and verified with simulation and measurements. General design procedures are also given in this paper in order to better understand the roles of the various critical components in the amplifier.