Evaluation of single-bit sigma-delta modulator DAC for electrical impedance spectroscopy

Abstract

In this paper, single-bit sigma-delta modulator based digital-analog conversion (DAC) is evaluated as potential driver in multichannel electrical impedance spectroscopy (EIS) arrays. The sinusoidal excitation with typical frequency range of a few Hz to a few MHz is a challenging task, which only very few state of the art implementations are even able to realize on chip, where the corresponding DAC consumes major amounts of area and power. Sigma-delta modulators offer signal generation with 1-bit representation, which could be advantageously multiplexed, distributed, and used on switches to generate analog output; thus its use could potentially lower the area and power consumption. This paper investigates the use of a single-bit sigma-delta DAC as direct driver for EIS experiments. Performances and limitations of the proposed system are experimentally analyzed and discussed. EIS experiments of micro-electrodes could be successfully conducted in a range from 20 Hz to 1 MHz and matched with reference measurements to better than 95 % accuracy.