Differential Sensing Circuit With Common-Mode Following Rejection
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Solution Overview
Problem
Differential circuits often fail to operate stably due to unpredictable variations in common mode voltage, leading to common mode noise, and existing feedback loops have limited bandwidth in addressing these variations, especially at higher frequencies.
Innovation Solution
A differential operation circuit that generates a reference voltage fluctuating with the common mode voltage, using this reference along with differential input signals to produce output signals with significantly reduced common mode noise, achieved through common mode following circuits and transistors configured to track and offset common mode components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a feedback loop is used to compensate for common mode voltage variations, then common mode rejection ratio is improved, but bandwidth is limited and high frequency rejection deteriorates
Solution Approach 1:
The patent introduces an intermediary common mode signal path that separately extracts and processes the common mode voltage component. By using a dedicated common mode input terminal and separate processing path, the circuit can compensate for common mode variations without interfering with the differential signal path, thereby achieving high common mode rejection across wide bandwidth without limiting the speed of the main differential operation.
2Stability of the object's composition
If common mode voltage is kept stable, then differential circuit operation stability is improved, but adaptability to varying common mode environments deteriorates
Solution Approach 1:
The patent implements feedback by continuously monitoring the common mode voltage through a dedicated common mode input terminal and automatically adjusting the differential output signals to compensate for detected common mode variations. This feedback mechanism allows the circuit to maintain stable differential operation across a wide range of common mode voltages, adapting to environmental changes while preserving operational stability.
3Device complexity
If traditional differential circuit design is used, then circuit simplicity is maintained, but common mode noise rejection capability deteriorates
Solution Approach 1:
The patent segments the differential circuit into distinct functional paths: a differential signal path for processing differential inputs, and a separate common mode signal path for detecting and compensating common mode variations. This segmentation allows each path to be optimized independently, achieving superior common mode noise rejection while maintaining relatively simple overall circuit structure through modular design.
Data Source
AI summary
A differential operation circuit that uses the differential input signals to generate a reference voltage that fluctuates with the common mode voltage of the differential input signals. The reference voltage includes a common mode component that generally follows the common mode voltage of the differential input signals. The common mode component of the reference voltage is used to fully or almost fully offset the common mode voltage of the differential input signals, thereby increasing the differential operation circuit's common mode rejection characteristics.