An Analysis of Small-Signal Source-Body Resistance Effect on RF MOSFETs for Low-Cost System-on-Chip (SoC) Applications

摘要

In this paper, we demonstrate a comprehensive analysis of small-signal source-body resistance (R{sub}(sb)) effect on the RF performances of RF MOSFETs for low-cost system-on-chip (SoC) applications for the first time. Our results show that for RF MOSFETs, both the kink phenomena of S{sub}11 and S{sub}22 become more obscure as reverse body bias (V{sub}B) increases due to the decrease of transconductance (g{sub}m). In addition, an increase of source-body spacing enhances both the kink phenomena of S{sub}11 and S{sub}22, but deteriorates the current-gain cut-off frequency (f{sub}T), maximum oscillation frequency (f{sub}(MAX)), and RF noise and power performances due to the increase of R{sub}(sb) of the devices. Analytical formulas are derived to explain the kink phenomena of S{sub}11 and S{sub}22, and to explain why increasing R{sub}(sb) leads to a reduction of equivalent substrate resistance R{sub}(sub) or worse f{sub}T, f{sub}(MAX), and RF noise performances of the devices. The present analyzes enable RF engineers to understand the S-parameters, noise parameters, and power performances of RF MOSFETs more deeply, and hence are helpful for them to optimize the layout of MOSFETs and to create a fully scalable RF CMOS model for SoC applications.