Robust derivative superposition method for linearising broadband LNAs

Abstract

A linearisation methodology for broadband low noise amplifiers (LNAs) is considered. The proposed scheme is composed of the main transistor operating in strong inversion healed by a couple of auxiliary transistors operating in triode and subthreshold regions. The nonlinearities of these transistors graciously and efficiently compensate each other, improving main transistor linearity by over 10 dB over all corners for input signals as large as −14 dBm. Power consumption increases by 6% while frequency response and input impedance are almost not affected because the compensating circuits are quite small compared with the main device. Simulation results show that the compensated LNA implemented in Jazz-Semiconductor 0.18 µm CMOS technology has a gain of 11.3 dB, IIP3=18.4 dBm, BW=3.6 GHz while drawing 7.4 mA from a 2.4 V supply voltage.