Sense Amplifier Switching for Neural Sensing Amid Stimulation Artifacts
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Solution Overview
Problem
Existing implantable neurostimulator devices face challenges in accurately sensing neural responses due to interference from stimulation artifacts, which complicate the detection of small-amplitude neural signals.
Innovation Solution
The implementation of differential sensing and common mode voltage stabilization techniques, combined with sense amplifier circuits, to isolate and amplify neural responses by subtracting common mode voltages and artifacts, allowing for precise neural signal detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional sensing methods are used in implantable neurostimulators, then the device structure remains simple, but the ability to accurately detect small-amplitude neural signals is compromised due to stimulation artifacts
Solution Approach 1:
The patent introduces a reference electrode as an intermediary element that captures the stimulation artifact signal. This reference signal is then used in a differential amplifier circuit to subtract the artifact from the neural signal, enabling accurate detection of small-amplitude neural responses despite the presence of large stimulation artifacts.
Solution Approach 2:
The patent converts the harmful stimulation artifact into a useful reference signal. By capturing the artifact through the reference electrode and using it in the differential amplification process, the system transforms the interference into a component that enables artifact rejection and improves neural signal detection accuracy.
2Measurement precision
If differential sensing with multiple electrodes is implemented, then neural signal detection accuracy improves, but the device complexity increases
Solution Approach 1:
The patent segments the sensing function into two distinct pathways: a main sensing electrode that captures both neural signal and artifact, and a reference electrode that captures primarily the artifact. This segmentation allows the differential amplifier to separately process and subtract the artifact component, achieving accurate neural signal detection with manageable circuit complexity.
Solution Approach 2:
The patent combines the signals from the main sensing electrode and reference electrode through a differential amplifier. By merging these two signal paths in a controlled manner, the system achieves artifact rejection while maintaining circuit simplicity, as the differential amplifier naturally performs the subtraction operation.
3Measurement precision
If high-gain amplification is used to amplify small neural signals, then signal detection capability improves, but noise and artifacts are also amplified
Solution Approach 1:
The patent performs preliminary action by capturing the artifact signal through the reference electrode before the amplification stage. The differential amplifier then subtracts this pre-captured artifact from the main sensing signal, ensuring that the high-gain amplification only amplifies the neural signal without simultaneously amplifying the artifact, thus avoiding noise and artifact amplification.
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
Enhances the ability to accurately sense neural responses, such as ECAPs and ERNA, by effectively distinguishing and amplifying these signals amidst stimulation artifacts, thereby improving therapeutic efficacy.
Implementation Method 1
sense amplifier circuitry comprising a first amplifier with a first input and a first output and a second amplifier with a second input and a second output... to isolate and amplify neural responses by subtracting common mode voltages and artifacts
Data Source
AI summary
Sense amplifier (amp) circuitry for an implantable stimulator device is disclosed useful for sensing neural responses or other voltages in a patient's tissue. The sense amp circuitry comprises a low-voltage and a high-voltage sense amp circuit, either of which may be selected based on an assessment of the magnitude of the voltage at either or both of the inputs connected to selected sensing electrodes. The assessed magnitude, as determined by monitoring circuitry, can be processed by an algorithm to select use of one of the sense amp circuits, selecting the low-voltage sense amp circuit when the magnitude(s) are lower, and the high-voltage sense amp circuit when the magnitude(s) are higher. Furthermore, DC offset compensation circuitry is disclosed to equate the DC levels of the inputs, which may only operate when the high-voltage sense amp is selected.