A Differential CMOS Common-Gate LNA Linearized by Cross-Coupled Post Distortion Technique

Abstract

A linearized differential common-gate CMOS low noise amplifier is proposed. The linearity is improved by a cross-coupled post distortion technique, employing auxiliary PMOS transistors in weak inversion region to cancel the third-order nonlinear currents of common-gate LNA and impair the second-order nonlinear currents of that. The negative conductance characteristic of cross-coupled auxiliary PMOS transistors improves the gain while the resulted NF is little affected. Furthermore, noise contribution and linearity deterioration from the cascode stage is eliminated by an inductor resonating with the parasitic capacitance observed at the source net of the cascode transistor. The LNA implemented in a 0.18 μm CMOS technology demonstrates that IIP3 and gain have about 8.2 dB and 1.4 dB improvements in the designed frequency band, respectively. The noise figure of 3.4 dB is obtained with a power dissipation of 6.8 mW under a 1.8 V power supply.