An Ultra-Low-Power Amplifier-Less Potentiostat Design Based on Digital Regulation Loop

Abstract

This paper presents a new potentiostat circuit architecture for interfaces with amperometric electrochemical biosensors. The proposed architecture, which is based on a digital low-dropout regulator (DLDO) structure, successfully eliminates the need for transimpedance amplifier (TIA), control amplifier, and other passive elements unlike other typical potentiostat topologies. It can regulate the required electrode voltages and measure the sensor currents ($\textit{I}_{\textit{SENSE}}$) at the same time by using a simple implementation with clocked comparators, digital loop filters, and current-steering DACs. Three different configurations of the proposed potentiostat are discussed including single-side regulated (SSR) potentiostat, dual-side regulated (DSR) potentiostat, and differential sensing DSR potentiostat with a background working electrode. These proposed potentiostats were designed and fabricated in a 180 nm complementary metal-oxide semiconductor (CMOS) process, occupying an active silicon areas of 0.0645 mm${}^{2}$, 0.1653 mm${}^{2}$, and 0.266 mm${}^{2}$, respectively. Validation results demonstrate that the proposed potentiostats operate on a wide sampling frequency range from 100 Hz to 100 MHz and supply voltage range from 1 V to 1.8 V. The proposed DSR potentiostat achieves a minimal power consumption of 3.7 nW over the entire dynamic range of 129.5 dB.