Chopped Auto-Zeroed Amplifier for Low-Noise Fast Sensor Settling
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Solution Overview
Problem
Existing amplifier designs for sensors, such as those used in Wheatstone bridge pressure sensors, face challenges with noise reduction and fast settling times, particularly in low input current applications, where direct current (DC) offset and noise from amplifiers can be significant.
Innovation Solution
A capacitively-coupled, chopped, auto-zeroed amplifier circuit is introduced, featuring a combination of chopping and auto-zeroing mechanisms with programmable gain and offset compensation, utilizing capacitors to minimize parasitic capacitance and optimize signal processing, allowing for faster settling and reduced noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If auto-zeroing and chopping mechanisms are implemented to reduce noise and DC offset, then noise level and DC offset are reduced, but settling time increases due to required time to settle after auto-zero phase and chopping state transitions
Solution Approach 1:
The patent implements dynamic switching between different operational phases (auto-zero phase, chopping phase, settling phase) to optimize performance. The amplifier transitions between these phases based on operational requirements, allowing it to achieve low noise and DC offset during signal processing while minimizing settling time through controlled phase transitions. This dynamic operation resolves the contradiction by making the system adaptable rather than static.
Solution Approach 2:
The patent employs periodic chopping action where the amplifier alternates between different chopping states at a specific frequency. This periodic modulation allows the system to achieve DC offset cancellation and noise reduction while maintaining fast settling characteristics through synchronized phase transitions. The periodic nature of the chopping operation enables predictable and optimized settling behavior.
2Power
If amplifier gain is increased to improve signal range, then output signal magnitude is improved, but noise and offset are also amplified
Solution Approach 1:
The patent applies preliminary auto-zeroing action before the main amplification process. During the auto-zero phase, the amplifier measures and stores offset voltages on capacitors before entering the signal amplification phase. This preliminary action removes DC offset components before they would be amplified, allowing high gain operation without proportionally amplifying offset errors. The chopping mechanism similarly pre-modulates the signal to separate AC signal components from DC offset components.
Solution Approach 2:
The patent introduces capacitors as intermediary elements to store offset voltages and feedback signals. These capacitors act as mediators that separate the offset cancellation function from the signal amplification function. By using capacitive coupling and feedback capacitors, the system can apply high gain to the signal while the capacitors selectively block or store DC offset components, preventing their amplification along with the signal.
3Device complexity
If fixed amplifier circuit configuration is used to simplify design, then device complexity is reduced, but adaptability for different gain and offset compensation requirements is limited
Solution Approach 1:
The patent implements a universal amplifier circuit that can perform multiple functions through a single integrated architecture. The same amplifier core is used for both signal amplification and offset cancellation through the chopping and auto-zeroing mechanisms. The feedback capacitors and switching network provide multi-functionality, allowing the circuit to operate in different modes (auto-zero phase, chopping phase, settling phase) without requiring separate dedicated circuits for each function.
Solution Approach 2:
The patent employs dynamic reconfiguration of the circuit through controlled switching between different phases and states. The amplifier can dynamically adjust its operating mode based on requirements, transitioning between auto-zeroing operation, chopping operation, and signal amplification. This dynamic adaptability allows a single fixed physical circuit to provide variable gain and offset compensation capabilities without requiring multiple fixed configurations.
Data Source
AI summary
In some embodiments, a circuit includes: a first chopping circuit configured to receive an input signal and generate a modulated signal responsive to the input signal; first and second input capacitors selectively coupled to receive a modulated signal or a common-mode voltage; an amplifier having an input and an output, the input coupled to the first and second input capacitors; an auto-zeroing circuit comprising one or more auto-zeroing feedback capacitors selectively coupled between the amplifier input and output; a gain selection circuit comprising one or more gain selection feedback capacitors coupled to the amplifier input and selectively coupled to the amplifier output or the common-mode voltage; an offset compensation circuit comprising one or more offset capacitors coupled to the amplifier input and selectively coupled to a reference voltage or the common-mode voltage; and a second chopping circuit configured to generate a demodulated signal responsive to the amplifier output.