A 0.6-µW Chopper Amplifier Using a Noise-Efficient DC Servo Loop and Squeezed-Inverter Stage for Power-Efficient...

Area of Science:

• Electrical Engineering
• Biomedical Engineering
• Analog Integrated Circuit Design

Background:

• Instrumentation amplifiers (IAs) are critical for neural and biopotential signal sensing.
• Existing IA designs often struggle with high power consumption and noise, limiting their application.
• DC servo loops (DSLs) and squeezed-inverter (SQI) stages are common but present noise and mismatch challenges.

Purpose of the Study:

• To develop an ultra-low-power and low-noise instrumentation amplifier for improved neural and biopotential signal sensing.
• To investigate and implement two novel design techniques to overcome limitations in existing IA architectures.
• To enhance signal acquisition quality in sensitive biomedical applications through advanced circuit design.

Main Methods:

• Implemented a noise-efficient DC servo loop (DSL) that reduces DSL noise contribution to 12.5% and eliminates the need for large capacitors.
• Utilized a squeezed-inverter (SQI) stage biased at 2VDSAT to increase bias current for noise reduction while maintaining low power.
• Employed a shared common-mode feedback (CMFB) loop to address mismatch issues in the SQI stage, achieving a high CMRR of 105 dB.

Main Results:

• Fabricated a capacitively-coupled chopper instrumentation amplifier (CCIA) using a 0.18-µm CMOS process.
• Achieved a low noise density of 88 nV/√Hz and an integrated noise of 1.5 µVrms.
• Demonstrated excellent performance with a noise efficiency factor (NEF) of 5.9 and a power efficiency factor (PEF) of 11.4.

Conclusions:

• The proposed design techniques effectively achieve ultra-low-power and low-noise performance for instrumentation amplifiers.
• The developed CCIA is highly suitable for sensitive neural and biopotential signal acquisition.
• The study presents a significant advancement in analog circuit design for biomedical applications.