Parasitic-Aware Analysis and Design of a Wideband gm-Boost Low Noise Amplifier at K-Band

Abstract

This brief presents a wideband low noise amplifier (LNA) at K-band. A parasitic-aware analysis focused on gain is proposed in the transformer feedback $g_{\mathrm {m}}$ -boost common-gate (CG) stage. This analysis models parasitic components as grounded equivalents, decoupling the amplifier into active circuitry and passive components. It addresses the design challenges of wideband amplifiers with complex capacitive networks, offering a more accurate representation of the amplifier’s characteristics and providing valuable guidance for parasitic-sensitive designs. The designed amplifier consists of a gm-boost transformer feedback CG stage followed by a capacitor-neutralized common source (CS) stage. An adapted interstage matching network is developed to compensate for the unbalanced transimpedance, which contributes to a flat overall wideband gain with a low noise figure (NF). The input and output of the LNA are well-matched and the LNA achieves a maximum gain of 14.6 dB, 3-dB bandwidth of 9.5 GHz (19-28.5 GHz), a minimum NF of 2.3 dB, and an input 1-dB compression point (IP1dB) exceeding -10.3 dBm across 19-28.5 GHz. The proposed LNA is implemented in a 110-nm CMOS process, occupying a compact chip area of 0.258 mm2 and consuming 25.6 mW at a supply voltage of 1.2 V. To the best of our knowledge, this brief represents the first comprehensive, parasitic-aware gain analysis of the transformer feedback $g_{\mathrm {m}}$ -boost CG stage.