Integration-Based Sensor Amplifier With Chopper Feedback for Low Noise
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Solution Overview
Problem
Existing amplifier circuits face challenges in achieving low-noise amplification of small signals while minimizing noise folding and noise performance, particularly in applications requiring high integration and low power consumption.
Innovation Solution
A semiconductor amplifier circuit with an integrator and feedback path that uses chopper modulation to separate signal noise, featuring a sample-and-hold block and feedback loop to reduce noise folding, allowing direct sampling without significant noise deterioration, and incorporating a second feedback loop for offset and flicker noise reduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If chopper modulation is used to eliminate offset and flicker noise, then noise performance is improved, but device complexity increases due to additional chopper circuits
Solution Approach 1:
The patent combines multiple chopper circuits (first chopper for signal path, second chopper for feedback path) into a unified amplifier structure where both chop independently at the same frequency. This merging approach achieves comprehensive noise rejection while sharing common control signals and timing, reducing overall system complexity compared to separate noise cancellation circuits.
Solution Approach 2:
The patent implements a feedback path with a second chopper that feeds back a portion of the output signal to the inverting input. This feedback mechanism actively cancels offset and flicker noise by continuously adjusting the feedback signal to counteract noise components, improving noise performance through dynamic compensation rather than static circuit elements.
2Measurement precision
If integration is used to amplify small signals, then signal amplification is improved, but noise folding increases due to sampling operations
Solution Approach 1:
The patent employs periodic chopper modulation at a specific frequency to periodically switch the signal path and feedback path. This periodic action modulates the signal to a higher frequency band before integration, preventing low-frequency noise folding during sampling while maintaining accurate signal amplification through the integrator circuit.
Solution Approach 2:
The patent changes the frequency parameter of the signal by using chopper modulation to shift the signal spectrum to higher frequencies before integration. This frequency transformation ensures that during subsequent sampling operations, noise folds to different frequency regions, reducing the impact of noise folding on the amplified signal accuracy.
3Area of stationary object
If high integration level is achieved in semiconductor device, then device miniaturization is improved, but power consumption increases due to additional active circuits
Solution Approach 1:
The patent designs the amplifier circuit where the integrator serves multiple functions: it amplifies small signals, filters noise, and works in conjunction with the chopper circuits for offset cancellation. The feedback path also serves dual purposes of signal transmission and noise reduction. This multi-functionality reduces the need for separate dedicated circuits, lowering overall power consumption while achieving high integration.
Solution Approach 2:
The amplifier circuit is designed to be self-regulating through the feedback mechanism where the second chopper automatically adjusts the feedback signal to cancel noise components. The circuit self-corrects for offset and flicker noise without requiring external calibration or additional control circuits, reducing power consumption by eliminating the need for separate adjustment mechanisms.
Data Source
AI summary
A semiconductor amplifier circuit comprising an input block adapted for receiving a voltage signal to be amplified, an integrator circuit having an integrating capacitor providing a continuous-time signal representative for the integral of the voltage signal, a first feedback path comprising: a sample-and-hold block and a first feedback block, the first feedback path providing a proportional feedback signal upstream of the current integrator. The amplification factor is larger than 1 for a predefined frequency range. Charge stored on the integrating capacitor at the beginning of a sample period is linearly removed during one single sampling period in such a way that the absolute value of the charge is smaller at the end of the sampling period than at the beginning of the sample period when the voltage signal to be amplified is equal to zero.