Low-Noise Current Readout Circuits: A tutorial overview

Low-noise current readout circuits are essential in modern scientific and industrial applications ranging from nanopore sensing to quantum systems. This tutorial-style paper presents a comprehensive analysis of key architectures for precision current sensing, including resistive and capacitive transimpedance amplifiers (R-TIAs and C-TIAs), as well as continuous-time current-input sigma-delta modulators (CT-CISDMs). It details the fundamental principles of current-to-voltage conversion, explores the stability and noise trade-offs in R-TIA designs, and examines the bandwidth (BW) and linearity benefits of C-TIAs. Additionally, it highlights the direct-digitization advantages of CT-CISDMs and briefly recaps current-to-frequency conversion techniques for ultralow-power applications. A comparative design example illustrates how each architecture balances performance metrics such as BW, noise, power efficiency, and integration complexity. Practical design guidelines and considerations for implementation under real-world constraints are also briefly discussed, providing a robust foundation for selecting the optimal front end for specific low-current sensing applications.