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Updated: Sep 2, 2025
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Published on: February 24, 2012
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Comparison and Integration of Voltage and Charge Amplifiers for Capacitive ECG Measurements
IEEE Transactions on Bio-Medical Engineering
|August 2, 2022
Summary
A novel switchable amplifier design offers adaptable bio-potential measurements by combining voltage (VA) and charge amplifier (CA) functionalities. This technology improves signal quality and estimates body-to-electrode capacitance without extra hardware.
Area of Science:
- Biomedical Engineering
- Electronic Instrumentation
- Wearable Technology
Background:
- Long-term, comfortable bio-potential measurements (e.g., ECG) are crucial for continuous health monitoring.
- Designing front-end amplifiers for capacitive electrodes presents challenges due to small body-to-electrode capacitance (Ce).
- Existing voltage amplifiers (VA) and charge amplifiers (CA) have limitations in handling artifacts and varying capacitance.
Purpose of the Study:
- To compare the artifact responses of voltage amplifiers (VA) and charge amplifiers (CA) for capacitive bio-potential sensing.
- To propose and validate a novel switchable VA-CA amplifier architecture.
- To enable passive estimation of body-to-electrode capacitance (Ce) using the proposed amplifier.
Main Methods:
- Implementation of a VA-CA switchable amplifier in a 180 nm CMOS process.
- Comparative analysis of VA and CA responses to motion and interference artifacts through modeling, simulation, and experimental testing.
- Validation of the Ce estimation method via electrical and in-vivo tests.
Main Results:
- Voltage amplifiers (VA) exhibit less sensitivity to Ce variations, while charge amplifiers (CA) demonstrate faster recovery from triboelectric artifacts.
- Artifacts in VA are multiplicative and modulated when simultaneous, whereas in CA, they remain independent.
- The implemented switchable amplifier successfully adapted to different signal conditions and artifact types.
Conclusions:
- The proposed VA-CA switchable amplifier offers superior adaptability compared to individual VA or CA designs.
- This architecture allows for optimal amplifier selection based on signal quality, Ce, and artifact presence.
- The system provides valuable insights into body-to-electrode interface quality (Ce) without requiring additional hardware.
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