Optimizing Low Noise Amplifiers: A Two-Stage Approach for Improved Noise Figure and Stability

Abstract

This study introduces a new design for a low noise amplifier (LNA) consisting of two stages taking advantage of the inherent lossy properties of the input matching components. By doing this, the design achieves a balance between the minimum noise figure (NF) and stability, eliminating the complexities and challenges introduced by feedback networks. Furthermore, the integration of the low-pass filter (LPF) into the design as a noise-matching network ensures improved performance across both the amplifier stages. A comprehensive analytical study is also introduced to delve deep into the relationship between critical LNA parameters, such as stability and noise figures, and the internal resistance of input-matching inductors. Two C-band LNAs are compared in terms of stability using indigenous 0.25µm GaN technology. The designs are substantiated by fabricating two LNA MMICs for a 5-7 GHz frequency range, having a minimum NF of 1.3 dB and 1.5 dB, with a gain of 15 dB and 16 dB at 6 GHz, respectively. The study reveals that using the proposed approach, there is an overall improvement in NF of 0.2 dB within the frequency of operation. The work entails a way to remove the feedback network in the LNA leading to an improved NF.INDEX TERMS C-Band, GaN, low-noise amplifier (LNA), low pass filter (LPF), noise figure (NF)