Chopper-Stabilized ECoG Amplifier Circuit for Low Noise and Small Die Area
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Solution Overview
Problem
Current brain-computer interface systems face challenges in designing amplifiers and digitizers for ECoG that require low input-referred noise while avoiding excessive loading of high impedance electrodes, leading to large die area and impractical array implementations due to the use of large passive components.
Innovation Solution
A novel circuit architecture using a chopper-stabilized, open-loop amplifier with a VCO-based ADC and mixed-signal feedback loop, employing capacitors for low 1/f noise cancellation and minimizing capacitance to reduce die area while maintaining power efficiency, allowing for compact and efficient neural signal acquisition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If large passive components are used in amplifier/digitizer design, then low input-referred noise and proper electrode loading are achieved, but die area becomes excessively large making array implementations impractical
Solution Approach 1:
The patent changes the operating parameters by using active feedback components instead of passive components, operating the amplifier at low supply voltage (0.5V-1.8V), and implementing chopper stabilization at specific frequencies to achieve low noise without large passive components. The feedback capacitor is dynamically controlled to provide offset cancellation while minimizing area.
Solution Approach 2:
The patent introduces a feedback path with a feedback capacitor and chopper stabilization circuit as intermediary elements between the amplifier input and output. This feedback mechanism mediates the offset and noise issues without requiring large passive components at the input, enabling compact design while maintaining signal quality.
2Measurement precision
If chopper stabilization is implemented to reduce noise and offset, then signal accuracy improves, but die area increases due to additional circuitry
Solution Approach 1:
The patent merges the chopper stabilization function with the offset cancellation feedback mechanism into a single integrated circuit block. The chopper-modulated feedback path combines noise reduction and offset cancellation functions, eliminating the need for separate circuits and reducing overall die area while maintaining measurement precision.
3Use of energy by moving object
If power consumption is reduced for implantable applications, then device efficiency improves, but noise performance and signal stability deteriorate
Solution Approach 1:
The patent uses periodic chopper modulation at optimized frequencies to achieve low noise and stable operation at low power consumption. The periodic switching action allows the circuit to operate efficiently in sleep and active modes while maintaining signal stability through synchronized sampling and processing.
Solution Approach 2:
The low-power amplifier circuit uses self-biasing techniques and automatic offset cancellation through feedback to maintain stable operation without requiring high power consumption. The circuit services its own stabilization needs through the feedback mechanism, reducing the power required for external stabilization components.
Data Source
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AI summary
Systems and methods for biosignal acquisition, and in particular, electrocorticography signal acquisition, are disclosed for small area, low noise recording and digitization of brain signals from electrode arrays.