An analog front-end enables electrical impedance spectroscopy system on-chip for biomedical applications

Abstract

The increasing number of applications of electrical bioimpedance measurements in biomedical practice, together with continuous advances in textile technology, has encouraged several researchers to make the first attempts to develop portable, even wearable, electrical bioimpedance measurement systems. The main target of these systems is personal and home monitoring. Analog Devices has made available AD5933, a new system-onchip fully integrated electrical impedance spectrometer, which might allow the implementation of minimum-size instrumentation for electrical bioimpedance measurements. However, AD5933 as such is not suitable for most applications of electrical bioimpedance. In this work, we present a relatively simple analog front-end that adapts AD5933 to a four-electrode strategy, allowing its use in biomedical applications for the first time. The resulting impedance measurements exhibit a very good performance in aspects like load dynamic range and accuracy. This type of minimum-size, system-on-chip-based bioimpedance measurement system would lead researchers to develop and implement light and wearable electrical bioimpedance systems for home and personal health monitoring applications, a new and huge niche for medical technology development.

Improving Performance and Versatility of Systems Based on Single-Frequency DFT Detectors Such as AD5933

“…Bioimpedance is another field, where DFT-based measurement systems have been developed [31][32][33][34], many targeting applications in functional textiles and wearable electronics [35][36][37][38]. Related systems include a miniaturized blood coagulation monitoring device developed in [39] and the biosensor platform described in [40].…”

AD5933-based spectrometer for electrical bioimpedance applications

“…Two different spectrometers have been used in this work: the ImpediMed SFB7 and a custom-made device based in the AD5933 in combination with an analog front-end to enable 4-electrode impedance measurements [3]. The measurements have been performed on a 2R1C parallel electrical model representing biological tissue, see Figure 1.…”

“…In this work the performance of a custom-made EBI spectrometer based on the AD5933 in combination with a 4-electrode Analog Front End [3] …”

Implantable bioimpedance monitor using ZigBee

“…The bioimpedance monitor is based in the 12 Bit Impedance Converter and Network Analyzer AD5933 [9], modified with an analog front-end that implements a 4-electrode measurement structure and allows to measure small impedances [10]. Basically the main modifications are the addition of a voltage controlled current source, to inject a constant current, a wide-bandwidth differential amplifier, and a voltage to current converter plus a voltage shifter to adapt to the single supply, 2-electrode structure of the device.…”