Graphical Design Approach for UWB Stacked CG LNA Using Inversion Coefficient

Abstract

The design of ultra-wide-band (UWB) low-noise amplifiers (LNAs) entails a large number of design challenges and tradeoffs, which include sustaining good input matching over a wide bandwidth along with finding a proper compromise between various LNA performance metrics, such as gain, bandwidth, noise figure, power, and linearity. This paper presents a design approach for UWB LNAs based on the inversion coefficient (IC). The proposed approach is a graphical design approach where the proper operating point is chosen based on predefined constraints. A complete systematic solution is presented for the problem of UWB input matching with a high degree of analytical accuracy. The design approach is illustrated through the design of two UWB stacked common-gate LNAs in 65 nm technology. The post-layout simulation results show very good agreement with analytical expectations. The first LNA achieves an S11 better than −8.2 dB over a 27.6 GHz frequency range, a gain of 12.4 dB over a 16.5 GHz bandwidth, a minimum noise-figure, NF, of 4.5 dB, and an IIP3 of −5.2 dBm while consuming only 530 μW. The second LNA achieves an S11 better than −15 dB over an 8.8 GHz frequency range, a gain of 12.5 dB over a 6.8 GHz bandwidth, a minimum NF of 4 dB, and an IIP3 of −4.3 dBm while consuming only 550 μW.