A Switchable Sub-3GHz/Sub-6GHz LNA With 0.4-1.1dB NF Using Triple-Feedback and Tunable Inter-Stage Matching Strategies

A broadband switchable low noise amplifier (LNA), supporting Sub-3GHz and Sub-6GHz modes for a wide range of wireless communication applications, is proposed. To achieve broadband simultaneous noise and impedance matching, a triple-feedback technique combined with a strategically designed inter-stage matching network (ISMN), is analyzed and developed. The dual-mode switchable functionality, offering wideband flat gain performance, is enabled through a switch-based tunable capacitor configuration within the ISMN with adjustable load impedance. Additionally, a current-reuse amplification topology is employed to enhance both gain and linearity while reducing power consumption. Fabricated using 250nm GaAs pHEMT technology, the proposed switchable LNA achieves gain of 21.7-24.2/18.7-21.7dB, noise figure (NF) of 0.4-0.96/0.65-1.1dB, output 1-dB compression point of 15.7-19.7/14.2-19.4dBm, and output third-order intercept point of 25.6-35.1/25.4-34dBm in Mode 1 (0.6-3.5GHz) and Mode 2 (0.6-5.5GHz), respectively. In comparison to Mode 1, the LNA operating in Mode 2 extends the 3-dB gain bandwidth by an additional 2GHz, at the cost of a 3 dB reduction in average gain, an increase of 0.15–0.25dB in NF, and a slight degradation in linearity.