Design of CMOS Analog Front-End Local-Field Potential Chopper Amplifier With Stimulation Artifact Tolerance for...

Area of Science:

• Biomedical Engineering
• Integrated Circuit Design
• Neuroscience Instrumentation

Background:

• Deep brain stimulation (DBS) systems require precise local-field potential (LFP) monitoring.
• Stimulation artifacts significantly corrupt LFP signals, hindering real-time analysis.
• Existing analog front-end (AFE) designs struggle with artifact removal and maintaining signal integrity.

Purpose of the Study:

• To develop a CMOS AFE LFP chopper amplifier with enhanced stimulation artifact tolerance.
• To improve signal linearity and reduce noise during concurrent stimulation and recording.
• To enable real-time closed-loop DBS system applications.

Main Methods:

• Implemented a chopper amplifier architecture in 0.18-μm CMOS technology.
• Utilized an analog template removal method for common-mode artifact voltage (CMAV) and differential-mode artifact voltage (DMAV) suppression.
• Incorporated an improved right-leg driven (RLD) circuit for common-mode noise reduction.
• Employed an improved auxiliary path to boost input impedance and manage artifact voltages.

Main Results:

• Achieved high input impedance (>133 MΩ in signal bandwidth, 8.2 GΩ at DC) via the improved auxiliary path.
• Demonstrated excellent common-mode rejection ratio (CMRR) of 131–144 dB with the improved RLD circuit.
• Measured low total harmonic distortion (THD) of 1.28% at the amplifier output under stimulation.
• Validated artifact tolerance with in vitro agar tests, showing 1.69% THD under constant current stimulation.

Conclusions:

• The proposed CMOS AFE LFP chopper amplifier effectively mitigates stimulation artifacts.
• The analog template removal method and improved circuit designs ensure signal linearity and noise suppression.
• The amplifier is well-suited for real-time closed-loop DBS system-on-chip (SoC) integration.