Multichannel Biopotential Readout Circuit for High Common-Mode Rejection
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Solution Overview
Problem
Existing multi-channel biopotential signal acquisition systems face challenges in reducing power consumption and maintaining a high common-mode rejection ratio, particularly due to the influence of poorly functioning electrodes which can affect amplifier performance.
Innovation Solution
The proposed read-out circuitry shares amplification of the reference signal across channels, utilizing a capacitor to define different cut-off frequencies for differential and common mode signals, and incorporates a buffer to prevent cross-talk, ensuring efficient power use and high common-mode rejection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a multichannel instrumentation amplifier design is used to reduce power consumption and number of parts, then power consumption is reduced by approximately 40 per cent, but input sections influence voltage at a shared point causing amplifier malfunction with badly functioning electrodes
Solution Approach 1:
The patent divides the reference signal processing into separate independent sections for each channel, with each input section having its own reference signal connection. This segmentation prevents a single faulty electrode from affecting the entire amplifier system, as each channel's reference signal path remains isolated and functional independently.
2Reliability
If an extra common-mode sense electrode is used to handle badly functioning electrodes, then electrode malfunction is managed, but common-mode rejection ratio is reduced
Solution Approach 1:
The patent creates multiple copies of the reference signal connection, with each channel having its own independent reference signal path. This allows each channel to independently reject common-mode signals without relying on a shared common-mode sense electrode, thereby maintaining high common-mode rejection ratio while handling electrode malfunctions through the redundant reference paths.
3Volume of moving object
If the sensor size is reduced to improve wearability and user experience, then the sensor can be integrated in a small patch, but power consumption control becomes more critical
Solution Approach 1:
The patent combines multiple reference signal connections into a single multichannel instrumentation amplifier architecture, reducing the total number of separate amplifier components needed. This merging achieves power consumption reduction of approximately 40 per cent compared to n independent one-channel amplifiers, enabling smaller sensor size while maintaining acceptable power levels.
Data Source
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AI summary
A read-out circuitry for acquiring a multi-channel biopotential signal, comprises: a plurality of read-out signal channels (120a-c; 220a-c; 320a-c; 420a-c), each receiving an input signal from a unique signal electrode (102); a reference channel (130; 230; 330; 430) receiving a reference signal from a reference electrode (102); wherein each read-out signal channel (120a-c; 220a-c; 320a-c; 420a-c) and the reference channel (130; 230; 330; 430) comprises a channel amplifier connected to receive the input signal in a first input node and with an output node connected to a second input node via a channel feedback loop; wherein each signal channel amplifier (122a-c; 222a-c; 322a-c; 422a-c) comprises a capacitor (124a-c; 224a-c; 324a-c; 424a-c) between the second input nodes of the signal channel amplifier (122a-c; 222a-c; 322a-c; 422a-c) and the reference channel amplifier (132; 232; 332; 432), and wherein each signal channel feedback loop and the reference channel feedback loop comprise a filter.