Differential Measuring Current Circuit for High-CMRR AC Sensing
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional AC current control technology for bioinformatics sensing faces issues such as accuracy and efficiency problems due to unmatched resistive components, low current efficiency, and challenges with common-mode rejection ratio (CMRR) in noisy environments, particularly in wearable devices.
Innovation Solution
A measuring current generation circuit with a setting resistor, transconductance amplifiers, and an output circuit that generates a cross-voltage and output current, allowing for differential input voltage control of current direction and frequency, eliminating the need for matching resistive components and grounding, thereby improving accuracy and efficiency while reducing passive components and noise susceptibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional AC current control technology is used, then current generation is achieved, but accuracy is seriously affected when resistive components do not match
Solution Approach 1:
The patent extracts and eliminates the need for trimming resistors and matching resistive components from the circuit. By using a transconductance amplifier-based architecture with differential inputs, the design removes the problematic passive components that caused accuracy issues, achieving high current accuracy without requiring component matching or additional trimming elements.
Solution Approach 2:
The patent replaces the conventional resistive component-based current control mechanism with a transconductance amplifier-based electronic control system. This substitution eliminates the need for physical resistor matching and trimming, using electronic amplification and differential signaling to achieve precise current control instead of relying on passive component tolerances.
2Productivity
If conventional AC current control technology is used, then current generation is achieved, but current efficiency is low since less than half of the generated current flows through the coupled output load
Solution Approach 1:
The patent inverts the conventional current flow architecture by using a differential output configuration where the current is pushed-pulled through the load. Instead of having current split and waste in conventional configurations, the inverted push-pull architecture ensures that nearly all generated current flows through the output load, achieving greater than 50% current efficiency by reversing the traditional current path arrangement.
3Object-affected harmful factors
If one terminal of the coupled output load is grounded in conventional technology, then circuit connection is simplified, but CMRR is low in environments with high common-mode noise
Solution Approach 1:
The patent employs asymmetric differential signaling where the two output terminals are driven with equal and opposite currents relative to a virtual ground, rather than grounding one terminal symmetrically. This asymmetric drive configuration creates common-mode rejection by ensuring that common-mode noise appears equally on both lines and is rejected by the differential measurement, achieving high CMRR without requiring one terminal to be physically grounded.
Solution Approach 2:
The patent creates a virtual ground reference by copying the common-mode voltage level to both output terminals through the transconductance amplifiers. This virtual copying of the reference level allows the circuit to reject common-mode disturbances while maintaining differential signal integrity, achieving high CMRR performance without the need for physical grounding of one terminal.
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 enhances current accuracy and efficiency, simplifies the circuit, and improves CMRR in noisy environments, enabling high-precision, low-current AC generation without the need for trimming resistors and grounding, suitable for wearable devices and multi-frequency input signals.
Implementation Method 1
a first transconductance amplifier TA0, a second transconductance amplifier TA1... The third input terminal and the fourth input terminal receive a differential input voltage signal and a cross-voltage of the setting resistor is generated
Data Source
AI summary
A measuring current generation circuit coupled to a setting resistor is disclosed. The generation circuit includes a first measuring terminal, a second measuring terminal, a first transconductance amplifier, a second transconductance amplifier and an output circuit. The first transconductance amplifier has a first input terminal and a second input terminal. The first input terminal is coupled to one terminal of the setting resistor. The second input terminal is coupled to another terminal of the setting resistor and coupled to the first measuring terminal. The second transconductance amplifier has a third input terminal and a fourth input terminal. The output circuit is coupled to output terminals of the first transconductance amplifier and the second transconductance amplifier respectively and has a first output terminal and a second output terminal. The first output terminal is coupled to the first input terminal. The second output terminal is coupled to the second measuring terminal.