A 3.6mW differential common-gate CMOS LNA with positive-negative feedback

Sanghyun Woo, Woonyun Kim, Chang-Ho Lee, Kyutae Lim, Joy Laskar

Abstract: A common-gate (CG) LNA has been widely investigated because it features superior bandwidth, linearity, stability, and robustness to PVT variations compared to a common-source (CS) topology [1]. In spite of these advantages, the dependence of gain and NF on the restricted transconductance (gm) renders this topology unsuitable for various wireless applications. The input impedance of a CG LNA is simplified as 1/gm, and the noise factor is inversely proportional to gm [2]. In order to achieve high gain and low NF, gm should be increased, which deteriorates the 50Ω input impedance matching for a conventional CG LNA.