Switched-Capacitor Neural Amplifier for DC Drift Suppression
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Solution Overview
Problem
Conventional neural-signal detecting circuits require large external DC shielding capacitors to suppress DC drift, leading to oversized circuits that limit the number of channels and measurement accuracy in micro-electrocorticographic scans, complicating system design and affecting physiological signal detection.
Innovation Solution
A neural-signal amplifier utilizing switched-capacitor circuits with differential and common-mode switches to switch between differential and common-mode amplifying states, replacing external capacitors and minimizing circuit size, while reducing leakage current and signal distortion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If external DC shielding capacitors are used to suppress DC drift, then DC drift suppression is improved, but circuit size increases
Solution Approach 1:
The patent merges the DC shielding capacitor function with the feedback capacitor by connecting the feedback capacitor between the output terminal and the inverting input terminal of the operational amplifier. This integration allows the same capacitor to serve both as the feedback element for signal amplification and as the DC shielding capacitor for suppressing DC drift, thereby eliminating the need for separate external capacitors and reducing overall circuit size.
Solution Approach 2:
The feedback capacitor in the operational amplifier circuit is designed to perform multiple functions simultaneously: it provides feedback for signal amplification and acts as a DC shielding capacitor to block DC drift. This multi-functional design reduces the number of external components needed and minimizes the overall circuit footprint while maintaining effective DC drift suppression.
2Power
If larger capacitance capacitors are used for shielding and amplification, then signal amplification is improved, but circuit complexity increases
Solution Approach 1:
The patent combines the feedback capacitor and DC shielding capacitor into a single component, reducing the number of external parts needed. This integration simplifies the circuit architecture while maintaining the required signal amplification capability through proper capacitor value selection and operational amplifier configuration.
Solution Approach 2:
The operational amplifier circuit is designed to use its own internal feedback capacitor to perform the DC shielding function, eliminating the need for separate external shielding capacitors. This self-service approach reduces circuit complexity and external component requirements while maintaining effective DC drift suppression and signal amplification.
3Reliability
If conventional neural-signal detecting circuit is used, then DC drift suppression is achieved, but the number of channels is limited
Solution Approach 1:
By integrating the DC shielding function into the feedback path of the operational amplifier, the circuit reduces the number of external components required per channel. This integration enables more channels to be implemented in a given space, increasing the scalability and versatility of the neural-signal detection system while maintaining effective DC drift suppression for each channel.
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
The solution allows for more accurate and flexible multi-channel neural signal acquisition with reduced distortion, adjustable detection range, and minimized power consumption, enhancing signal gain and system integration.
Implementation Method 1
a first capacitor C1 connected between the inverting input terminal and a first switching unit, and a second capacitor C2 connected between the non-inverting input terminal and a second switching unit
Implementation Method 2
an operational amplifier, a first capacitor C1 connected between the inverting input terminal and a first switching unit
Data Source
AI summary
A neural-signal amplifier includes an amplifier, a switched-capacitor circuit-input unit, a switched-capacitor feedback-circuit unit, and a switched-capacitor circuit-output unit. Each of the switched-capacitor circuit-input unit, the switched-capacitor feedback-circuit unit, and the switched-capacitor circuit-output unit includes a plurality of differential switches, a plurality of common mode switches, and a plurality of capacitors. By controlling the switches to turn on or performing the switched-capacitor operation, the neural-signal amplifier is controlled to suppress the DC drift and reconstruct the DC input of the common-mode power supply.