Neuromodulation Amplifier Circuit With Common-Mode Feedback Suppression

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Conventional neuromodulation devices face challenges in suppressing common mode (CM) voltage signals and reducing CM interference (CMI), which can lead to amplification failures due to limited CM range and input impedance degradation when additional CM feedforward amplifiers are used.

Innovation Solution

The proposed amplifier circuit incorporates a CM amplifier that combines and amplifies CM voltage signals with an inverting gain, providing an inverted CM voltage signal to the transconductor to suppress CM interference without degrading the input impedance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Object-affected harmful factors

If a CM feedforward amplifier is inserted to suppress common mode voltage signals, then CM interference is reduced, but input impedance is degraded and device complexity increases

Engineering Contradiction:

ImproveCM interferenceVSAvoidamplifier circuit complexity

Core Design Contradiction:

Object-affected harmful factorsVSDevice complexity

Solution Approach 1:

The amplifier circuit is divided into distinct functional modules: an input stage with capacitive coupling for DC blocking, a differential transconductor for signal amplification, and a feedback stage with separate CM and DM feedback paths. This segmentation allows each module to be optimized independently, reducing overall complexity while maintaining CM suppression capability.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The feedback amplifier is designed to simultaneously provide both common mode feedback and differential mode feedback functions through a unified structure. The feedback network handles both CM and DM signals, eliminating the need for separate dedicated CM feedforward amplifier circuits and reducing device complexity.

Inventive Principle:

Principle #6Universality (Multi-functionality)

2Object-affected harmful factors

If a CM feedforward amplifier is inserted to suppress common mode voltage signals, then CM interference is reduced, but input impedance is degraded

Engineering Contradiction:

ImproveCM interferenceVSAvoidinput impedance

Core Design Contradiction:

Object-affected harmful factorsVSReliability

Solution Approach 1:

A feedback amplifier is introduced as an intermediary element that indirectly suppresses CM interference by feeding back CM voltage signals to the input nodes. This approach avoids direct insertion of CM feedforward amplifiers that would degrade input impedance, while still achieving effective CM rejection through the feedback mechanism.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The circuit employs feedback amplifiers to detect and counteract common mode voltage signals by feeding back inverted CM voltages to the input terminals. This feedback mechanism suppresses CM interference dynamically without requiring additional input capacitors that would degrade input impedance, maintaining both CM rejection and input impedance stability.

Inventive Principle:

Principle #23Feedback

3Object-affected harmful factors

If additional input capacitors are added for CM suppression, then CM voltage fluctuations are minimized, but chip area increases

Engineering Contradiction:

ImproveCM voltage fluctuationsVSAvoidchip area

Core Design Contradiction:

Object-affected harmful factorsVSArea of stationary object

Solution Approach 1:

The feedback amplifier serves multiple functions simultaneously: it provides CM suppression, DM amplification, and impedance buffering. This multi-functionality eliminates the need for additional dedicated CM suppression capacitors, reducing chip area while maintaining effective CM voltage fluctuation suppression through the feedback mechanism.

Inventive Principle:

Principle #6Universality (Multi-functionality)

4Reliability

If impedance boosting network is incorporated to compensate for impedance degradation, then input impedance is restored, but hardware complexity and chip area increase

Engineering Contradiction:

Improveinput impedanceVSAvoidhardware complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The feedback amplifier inherently provides impedance buffering to the input nodes through its high input impedance configuration. This self-service mechanism automatically compensates for any impedance degradation without requiring external impedance boosting networks, maintaining input impedance stability while avoiding additional hardware complexity.

Inventive Principle:

Principle #25Self-service

Data Source

PatentUS20250073450A1Common Mode Interference Suppression In An Amplifier Circuit For A Neuromodulation Device

Publication Date: 2025.03.06 INTERUNIVERSITAIR MICRO ELECTRONICS CENT (IMEC VZW)

AI summary

The present disclosure provides a neuromodulation device that comprises at least one amplifier circuit that suppresses a common mode (CM) voltage signal in the input voltage signal. The amplifier circuit comprises an input stage to receive the input voltage signal, and a differential transconductor to provide an output current signal based on a DM voltage signal in the input voltage signal. The transconductor is provides a first CM voltage signal tapped after a non-inverting input, and a second CM voltage signal tapped after am inverting input, to CM amplifier of the amplifier circuit. The CM amplifier combines the first CM voltage signal with the second CM voltage signal, amplifies the combined CM voltage signal with an inverting gain, and provides the inverted CM voltage signal back to the non-inverting input and the inverting input of the transconductor for enabling the CM suppression.