Load Evolution and Gain/Linearity Trade-off Mechanisms in High-Performance Single-Stage Amplifiers

This article systematically reviews the development path of high-performance single-stage amplifiers under low-voltage constraints. First, leveraging the superposition principle and physical equivalent models, this paper clarifies the physical mechanisms of circuit nonlinearity and the physical connotation of impedance characteristics. Subsequently, it systematically discusses the evolutionary logic of load techniques: it analyzes the “gain–swing deadlock” caused by traditional resistive loads, examines how active loads realize impedance decoupling, and further derives inverter-based current-reuse architectures. In response to the recent demand for ultra-low-power design, it focuses on application strategies of inverter-based structures at 0.3 V ultra-low supply voltage and in the subthreshold region. This paper further investigates linearization techniques centered on source degeneration and comparatively studies the trade-off between resistive degeneration and active degeneration in terms of noise characteristics and area efficiency. The survey indicates that combining inverter-based current-reuse topologies with active linearization techniques is a key trend for future high-energy-efficiency.