Capacitive Sensor Amplifier Circuit for Low-Noise Detection
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing sensor devices that detect voltage changes in electrostatic capacitance face challenges with low detection voltage and noise amplification, which affect detection accuracy.
Innovation Solution
A sensor device incorporating a capacitive amplifier circuit with a first and second capacitor connected in series, amplifying the detection voltage based on capacitance ratio to improve signal quality and reduce noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a source follower is used to detect voltage generated in a detection electrode, then the detection voltage can be amplified, but noise components are also amplified along with the detection voltage
Solution Approach 1:
The patent divides the amplification process into two distinct stages: first, a capacitive amplifier circuit amplifies only the detection voltage signal without amplifying noise; second, a source follower amplifies the already-amplified signal. This segmentation allows selective amplification of the signal while controlling noise amplification, resolving the contradiction between detection accuracy and noise amplification.
Solution Approach 2:
The capacitive amplifier circuit performs preliminary amplification of the detection voltage before the signal is passed to the source follower. By amplifying the signal first, the subsequent noise amplification by the source follower becomes less significant relative to the signal level, thereby improving signal-to-noise ratio and detection accuracy.
2Quantity of substance
If the detection voltage is minute, then the detection electrode can operate with small signal, but the subsequent amplification stage must amplify both signal and noise
Solution Approach 1:
The patent segments the amplification function into two specialized stages: the capacitive amplifier dedicated to initial signal amplification and the source follower for subsequent buffering and amplification. This segmentation allows the first stage to optimize for signal amplification while the second stage handles other functions, preventing noise amplification from degrading the signal-to-noise ratio.
Solution Approach 2:
The capacitive amplifier circuit acts as an intermediary between the detection electrode and the source follower. It conditions the minute detection voltage by amplifying it to a suitable level before passing it to the source follower, thereby preventing the source follower from having to amplify both the minute signal and associated noise simultaneously.
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 enhances detection accuracy by reducing noise and increasing the signal-to-noise ratio, simplifying the system configuration, and reducing process costs through improved voltage amplification.
Implementation Method 1
a capacitive amplifier circuit having a first capacitor and a second capacitor connected in series to each other, and configured to detect the voltage generated in the detection electrode and output a detection signal obtained by amplifying the voltage generated in the detection electrode based on a capacitance ratio between the first capacitor and the second capacitor
Implementation Method 2
a detection electrode opposing an external electrode to which a predetermined voltage is applied, and configured to generate a voltage corresponding to a change in electrostatic capacitance
Data Source
AI summary
To reduce effects of noise and improve detection accuracy, a sensor device includes: a detection electrode opposing an external electrode to which a predetermined voltage is applied, and configured to generate a voltage corresponding to a change in electrostatic capacitance; and a capacitive amplifier circuit having a first capacitor and a second capacitor connected in series to each other, and configured to detect the voltage generated in the detection electrode, and output a detection signal obtained by amplifying the voltage generated in the detection electrode based on a capacitance ratio between the first capacitor and the second capacitor.