AC instrumentation amplifier for bioimpedance measurements

Area of Science:

• Biomedical Engineering
• Electrical Engineering
• Signal Processing

Background:

• Bioimpedance measurements are vital for assessing tissue properties.
• Electrode-skin contact impedance, particularly its capacitive elements, significantly impacts measurement accuracy.
• Existing instrumentation amplifiers often struggle to meet the stringent requirements for precise bioimpedance analysis.

Purpose of the Study:

• To analyze the input impedance and Common-Mode Rejection Ratio (CMRR) requirements for amplifiers used in bioimpedance measurements.
• To present an AC-coupled instrumentation amplifier (IA) design that addresses these specific needs.
• To demonstrate interference and noise reduction capabilities, alongside achieving zero phase shift over a broad frequency range.

Main Methods:

• Analysis of capacitive electrode-skin contact impedance effects on amplifier requirements.
• Design and simulation of an AC-coupled instrumentation amplifier (IA).
• Evaluation of the IA's performance regarding input impedance, CMRR, noise, and phase shift across various frequencies.

Main Results:

• The proposed AC-coupled IA meets the critical input impedance and CMRR requirements for bioimpedance measurements.
• The design successfully reduces interference and noise.
• A zero phase shift is maintained over a wide frequency band without necessitating expensive broadband operational amplifiers.

Conclusions:

• The developed AC-coupled instrumentation amplifier is suitable for accurate bioimpedance measurements.
• The design offers a robust solution for mitigating electrode-skin impedance challenges.
• This amplifier provides a cost-effective and high-performance alternative for bioimpedance sensing applications.