Switched-Capacitor Integrator With Charge Subtraction Against Saturation
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Solution Overview
Problem
Integrator circuits often saturate when measuring voltages that are approximately the same as the reference voltage, leading to unreliable output.
Innovation Solution
A switched-capacitor integrator circuit with a smaller capacitor coupled in parallel to the sampling capacitor, where both capacitors are charged during the sampling phase and the terminals of the smaller capacitor are swapped during the integration phase to subtract a portion of the sample charge, compressing the dynamic range of the input signal and preventing saturation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the integrator measures a voltage that is approximately the same as the reference voltage, then the measurement capability is improved, but the integrator becomes saturated and output reliability deteriorates
Solution Approach 1:
The sampling capacitor is divided into two segments: the original sampling capacitor and a smaller capacitor coupled in parallel. During the sampling phase, both capacitors are charged together. During the integration phase, the smaller capacitor's terminals are swapped to subtract a portion of the sample charge from the sampling capacitor. This segmentation allows the integrator to handle input voltages close to the reference voltage by preventing saturation through charge subtraction.
2Reliability
If the dynamic range of the input signal is compressed, then saturation is prevented and output reliability is improved, but the circuit complexity increases due to additional capacitors and switching
Solution Approach 1:
A smaller capacitor is coupled in parallel with the sampling capacitor, merging two capacitive elements into a single functional unit. During the sampling phase, both capacitors are charged simultaneously through the same switch network. During the integration phase, the smaller capacitor's terminals are swapped to provide charge subtraction. This merging approach compresses the dynamic range of the input signal to prevent saturation while adding minimal circuit complexity compared to more elaborate saturation-prevention schemes.
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 effectively prevents saturation by reducing the input voltage level relative to the reference voltage, ensuring accurate and reliable output without increasing silicon area or power consumption.
Implementation Method 1
a smaller capacitor coupled in parallel with a sampling capacitor. During the sampling phase, both the sampling capacitor and the smaller capacitor are charged
Data Source
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AI summary
An integrator circuit includes: an operational amplifier; a first capacitor coupled to an input of the operational amplifier; a second capacitor coupled in parallel to the first capacitor so that a first terminal of the first capacitor is configured to be electrically coupled to a first terminal of the second capacitor by a first switch; and a second switch configured to electrically couple the first terminal of the second capacitor to a second terminal of the first capacitor.