MOS_CS_LNASheet 1 of 11 MOS COMMON-SOURCE LNA Design Tutorial J P Silver E-mail: john@rfic.co.uk 1 ABSTRACT This tutorial describes the theory and design on a MOS Low noise amplifier using source degeneration. Source degeneration offers lower noise figures ~2-3dB than the Common-gate LNA topographies (with NF of ~5dB). Design theory and the relevant equations are given, with a worked example using Agilent ADS simulation circuits and plots. Zin M2 Vbias Rs M1 2 INTRODUCTION 3 INDUCTIVE SOURCE DEGENERATION INPUT MATCHING Previous design examples have assumed that the input is resistive and offered the best value of source resistance (Rs) to obtain best noise match. In reality the input of the device is reactive, with a real and capacitive impedance. Figure 1 shows the equivalent model of a MOSfet, c……