Multi-Frequency Chopper Amplifier for Low-Ripple Noise Reduction
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Solution Overview
Problem
Conventional instrumentation amplifiers face challenges with noise aliasing and limited bandwidth in discrete time architectures, and high ripple in chopper-stabilized designs, particularly in low power applications, which affect the accuracy of measurement signals.
Innovation Solution
A chopper-stabilized amplifier utilizing a multi-frequency chopping signal to modulate the input signal, reducing chopping artifacts by translating DC offset and flicker noise to higher frequencies, thereby reducing amplitude and allowing less stringent filtering requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a discrete time switched capacitor architecture is used, then the amplifier can obtain discrete signal samples, but it produces undesirable aliasing of noise and signals
Solution Approach 1:
The patent introduces an anti-aliasing filter as an intermediary component between the input signal and the switched capacitor circuit. This filter preprocesses the input signal to remove frequency components that would cause aliasing, thereby eliminating the harmful aliasing effect while preserving the signal sampling capability of the discrete time architecture.
2Measurement precision
If a chopper stabilized architecture is used, then amplifier noise and offset errors are minimized, but the bandwidth is limited producing large ripple in the passband
Solution Approach 1:
The patent employs dynamic element matching (DEM) technology that randomly switches the positions of capacitors in the chopper stabilized amplifier circuit during operation. This dynamic switching distributes the ripple energy across multiple frequency components, effectively reducing the peak ripple amplitude in the passband while maintaining the noise and offset performance benefits of chopper stabilization.
3Measurement precision
If a chopper circuit up-modulates the measurement signal to a higher frequency band, then noise and offset errors are minimized, but chopping artifacts are introduced
Solution Approach 1:
The patent segments the single chopping operation into multiple chopping phases by using multiple capacitors switched at different times and frequencies. This segmentation distributes the chopping artifacts across multiple frequency components rather than concentrating them at a single frequency, thereby reducing the amplitude of individual artifacts while maintaining the overall noise and offset reduction benefit.
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 multi-frequency chopping signal effectively reduces chopping artifacts, maintaining signal integrity and allowing for broader bandwidth while minimizing noise and offset, enhancing the accuracy of measurement signals in medical sensing applications.
Implementation Method 1
The first modulator is configured to modulate the amplitude of a differential input signal at multiple frequencies using a plurality of first modulator switches driven by non-overlapping signals, φ1 and φ2
Implementation Method 2
The differential amplifier is configured to amplify the differential modulated signal received at the positive input and negative input to produce a differential amplified signal
Implementation Method 3
The first switched feedback path is switched by the non-overlapping signals, φ1 and φ2. The second switched feedback path is switched by the non-overlapping signals, φ1 and φ2
Data Source
AI summary
A chopper stabilized amplifier that utilizes a multi-frequency chopping signal to reduce chopping artifacts. By utilizing a multi-frequency chopping signal, the amplifier DC offset and flicker noise are translated to the higher chopping frequencies but are also smeared, or spread out in frequency and consequently lowered in amplitude. This lower amplitude signal allows for less stringent filtering requirements.