Dual-mode CMOS analog front-end (AFE) for electrical impedance spectroscopy (EIS) systems

Area of Science:

• Electrical Engineering
• Biomedical Engineering
• Analog Integrated Circuit Design

Background:

• Electrical Impedance Spectroscopy (EIS) is a powerful non-invasive technique for characterizing biological tissues and cells.
• Existing EIS systems often lack flexibility in readout channels, limiting their application scope for simultaneous multi-scale analysis.
• There is a growing need for integrated solutions that support both bipolar and tetrapolar measurements for diverse bioimpedance applications.

Purpose of the Study:

• To present the design and simulated performance of a novel dual-mode wideband CMOS analog front-end (AFE) for EIS.
• To enable flexible and real-time simultaneous analysis of both single cells and large-scale tissues/organs.
• To provide integrated current-readout (CR) and voltage-readout (VR) channels optimized for various EIS configurations.

Main Methods:

• Designed a CMOS AFE integrating two CR channels and four VR channels.
• Implemented a 2-bit control for VR channel gain and bandwidth selection.
• Incorporated an automatic gain control (AGC) unit for CR channels to manage signal range.
• Conducted post-layout simulations to evaluate channel performance and power consumption.

Main Results:

• The VR channel achieves wideband operation up to 12 MHz with a low noise floor of 16.4 nV/Hz1/2.
• The CR channel offers an 80 dB dynamic range for currents from 1 nA to 10 μA, with a noise floor of 1.4 pA/Hz1/2.
• The chip operates from a 1.8 V supply, consuming 290–690 μA per channel.
• VR and CR channels occupy small areas (0.48 mm2 and 0.21 mm2, respectively).

Conclusions:

• The developed dual-mode CMOS AFE provides a flexible and high-performance solution for EIS.
• The integrated CR and VR channels support both bipolar and tetrapolar configurations for versatile bioimpedance measurements.
• This AFE is suitable for real-time, simultaneous analysis across different biological scales, from single cells to organs.