An Auto-Zero Stabilized Voltage Buffer with a Quiet Chopping Scheme and Constant Input Current

📋 论文概要

本文提出了一种采用静音斩波方案的自稳零电压缓冲器，通过优化占空比的自稳零稳定环路，解决了传统自稳零缓冲器低频噪声高和输入电流随输入电压变化的问题，实现了低噪声和恒定输入电流。

💡 主要创新点

• 提出静音斩波（Quiet Chopping）方案并结合自稳零稳定环路，有效降低低频噪声密度。
• 通过优化占空比，使自稳零缓冲器的低频噪声密度从原来的√5倍降低至与传统结构相当的水平。
• 实现了与输入电压无关的恒定输入电流，改善了高阻抗传感器读出的稳定性。

🏷 关键词

📄 原文摘要

The readout of high-impedance sensors and sampled voltage references [1] requires amplifiers that can achieve both low offset and low input current. Recently, it has been shown that this unique combination can be achieved by an auto-zero (AZ) stabilized buffer [2]. However, its low-frequency noise density is √5 times higher than the buffer’s own white-noise voltage spectral density en. Furthermore, its input current is not constant, but varies significantly with the input voltage. To overcome the first issue, a chopped AZ stabilization loop with an optimized duty-cycle is proposed to bring the low-frequency noise density close to √2en, the fundamental limit of an AZ stabilized amplifier. The second issue is solved by replacing the transmission-gate input switches used in [2] with NMOS switches and a constant Vgs drive. This keeps their charge injection constant over a wide input voltage range, and results in a constant input current.

👥 作者与机构

Thije Rooijers, Johan H. Huijsing, Kofi A. A. Makinwa

Delft University of Technology, Delft, The Netherlands