EEG Electrode Array With Feedback Amplifier for Common Mode Rejection
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Solution Overview
Problem
Existing EEG systems rely on differential amplifiers that require delicate resistor balancing to achieve high common mode rejection, which is difficult to maintain over time and varying conditions.
Innovation Solution
An active electrode array that uses a feedback amplifier to set the common average signal to zero, eliminating the need for differential amplifiers and allowing common mode rejection without resistor balancing, using a feedback operational amplifier to maintain a virtual ground and reject common mode signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If differential amplifiers with laser trimmed resistors are used to achieve high common mode rejection ratio, then the common mode rejection ratio is improved, but the system cannot remain balanced over time and varying operating conditions
Solution Approach 1:
The patent employs a feedback amplifier that continuously monitors the common mode voltage and adjusts the reference electrode potential to maintain zero common mode voltage. This feedback mechanism dynamically compensates for drift and environmental changes, ensuring stable common mode rejection without requiring delicate resistor balancing that degrades over time.
Solution Approach 2:
The system uses the reference electrode itself as an active element that automatically adjusts its potential through the feedback amplifier to counteract common mode disturbances. This self-regulating mechanism eliminates the need for external calibration or manual balancing, allowing the system to maintain optimal performance autonomously under varying conditions.
2Measurement precision
If delicate resistor balancing is performed to achieve accurate differential amplification, then the common mode rejection ratio is improved, but the complexity and difficulty of maintaining balance increases
Solution Approach 1:
Instead of relying on precise passive resistor matching, the invention introduces an active feedback amplifier that continuously adjusts the reference potential to maintain common mode rejection. This replaces the complex requirement for delicate resistor balancing with a simpler active control system that is easier to manufacture and maintain.
Solution Approach 2:
The system transitions from a passive resistive balance approach to an active voltage control approach. By changing the reference electrode potential dynamically through the feedback amplifier, the system achieves common mode rejection through parameter adjustment rather than fixed component matching, simplifying the overall device complexity.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution provides reliable and consistent common mode rejection, eliminating the need for traditional differential amplifiers and resistor balancing, resulting in cleaner EEG signals with high common mode rejection ratios, even in varying conditions.
Implementation Method 1
a feedback amplifier providing the output signal based on a difference between ground and a combined average signal of an output signal of each of the plurality of electrodes
Data Source
AI summary
An electrode array for EEGs is described that includes a feedback amplifier driving one of the electrodes. Use of the feedback amplifier can eliminate the need to use precisely balanced resistors in a differential amplifier as well as allowing the elimination of a reference electrode and ground electrode.