A Bidirectional Current-Mirror Based Potentiostat Using a Slice-Based Class-AB Amplifier

TL;DR

This paper introduces a highly sensitive, low-power bidirectional potentiostat with a slice-based class-AB amplifier for electrochemical sensing, achieving a wide dynamic range and low detectable current.

Contribution

It presents a novel slice-based class-AB amplifier design enabling bidirectional current sensing over five decades with low power consumption and high efficiency.

Findings

Minimum detectable current of 91.7 pA

Dynamic range of 147 dB for sensor currents

Power consumption between 14.1 μW and 39.3 μW

Abstract

A pico-ampere sensitive electrochemical sensor signal acquisition chain consisting of a multi-channel bidirectional current-mirror based potentiostat and a multiplexed current-input delta-sigma ($\Delta \Sigma$) ADC is presented. Slice-based class-AB amplifiers with output stage current replication using reconfigurable current-mirrors enable bidirectional current sensing over a range of five decades. The replicated current is digitized by the ADC. The proposed circuit achieves a minimum detectable current of 91.7 pA, resulting in a dynamic range of 147 dB for sensor currents up to $\pm$1 mA. The potentiostat is operated at a 3 V supply, the ADC at 1.5 V. The static power consumption of a single interface channel depends on the number of active amplifier slices and is between 14.1 $\mu$W and 39.3 $\mu$W. The highest power efficiency among similar systems and the low voltage headroom consumption of less than 500 mV enables a versatile use of the interface for multiple sensing applications.