The Design of Low Noise Amplifiers in Deep Submicron CMOS Processes: A Convex Optimization Approach

Abstract

With continued process scaling, CMOS has become a viable technology for the design of high-performance low noise amplifiers (LNAs) in the radio frequency (RF) regime. This paper describes the design of RF LNAs using a geometric programming (GP) optimization method. An important challenge for RF LNAs designed at nanometer scale geometries is the excess thermal noise observed in the MOSFETs. An extensive survey of analytical models and experimental results reported in the literature is carried out to quantify the issue of excessive thermal noise for short-channel MOSFETs. Short channel effects such as channel-length modulation and velocity saturation effects are also accounted for in our optimization process. The GP approach is able to efficiently calculate the globally optimum solution. The approximations required to setup the equations and constraints to allow convex optimization are detailed. The method is applied to the design of inductive source degenerated common source amplifiers at the 90 nm and 180 nm technology nodes. The optimization results are validated through comparison with numerical simulations using Agilent's Advanced Design Systems (ADS) software.