Power constrained SiGe/SOI sub 6GHz LNA design analysis and comparison

In this paper, we first analyze an LNA core, cascode structure cut off frequency and power gain relationship with device parameters. Then we discuss the LNA design differences between FET LNA and SiGe LNA during design optimization. SOI floating body FETs have advantages in higher Ft in the optimized current biased region and can offer more design flexibility, while SiGe NPNs need much less trade off room. With this design methodology, we design 5GHz LNAs based on 120nm SOI FET and 0.12um SiGe NPN with 5mA current limitation. The SOI NFET LNA achieves 16dB gain and 1.2dB NF, while SiGe achieves 20dB gain and <1dB NF.