Capacitive Sensor Feedback Circuit to Reduce Parasitic Signal Loss
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Solution Overview
Problem
Existing sensor arrangements, such as those using capacitive sensors like microphones, face signal attenuation issues due to parasitic capacitors, which hinder the efficient generation of amplified sensor signals based on capacitance changes.
Innovation Solution
A sensor arrangement comprising an amplifier with a series connection of a capacitive sensor and a feedback capacitor, where the voltage source is connected to a feedback node between the sensor and the feedback capacitor, generating an inverted amplified signal with high efficiency, and utilizing a biasing circuit for gain control and noise reduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional sensor arrangement with charge pump and preamplifier is used, then the sensor signal can be amplified, but parasitic capacitors cause signal attenuation
Solution Approach 1:
The patent extracts and eliminates the charge pump component from the conventional sensor arrangement. By removing the charge pump, the source of parasitic capacitance is eliminated, thereby preventing signal attenuation while maintaining the amplification function through a simplified direct coupling architecture
Solution Approach 2:
The patent converts the harmful effect of parasitic capacitors into a beneficial configuration by repositioning the feedback capacitor connection. The feedback capacitor is connected directly to the amplifier input without passing through a charge pump, transforming what would be a source of attenuation into a component that provides stable feedback without introducing parasitic effects
2Reliability
If more components are added to the sensor arrangement, then signal amplification and control can be improved, but device complexity increases
Solution Approach 1:
The patent merges the functions of the charge pump and preamplifier into a single direct coupling stage. The sensor output is directly coupled to the amplifier input, eliminating the need for separate charge pump and preamplifier components while maintaining signal amplification quality through proper feedback capacitor configuration
Solution Approach 2:
The feedback capacitor serves multiple functions simultaneously: it provides signal feedback for amplification, sets the gain of the amplifier, and compensates for input capacitance effects. This multi-functionality eliminates the need for separate components, reducing overall device complexity while maintaining reliability
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
This configuration achieves a cost-effective, low-component-count solution for generating amplified sensor signals with high signal-to-noise ratio and reduced total harmonic distortion, suitable for capacitive sensors like MEMS microphones, with improved sensitivity and reduced parasitic effects.
Implementation Method 1
The quantity that is to be measured changes the capacitance value of the capacitive sensor
Implementation Method 2
A series connection of the capacitive sensor and a feedback capacitor couples the signal output to the signal input
Data Source
Figure 1A~1B
Figure 1C~1D
Figure 1E
AI summary
A sensor arrangement (10) comprises an amplifier (11) having a signal input (12) to receive an input signal (SIN) and a signal output (13) to provide an amplified sensor signal (SOUT) that is an inverted signal with respect to the input signal (SIN). Furthermore, the sensor arrangement (10) comprises a series connection of a capacitive sensor (14) and a feedback capacitor (15), wherein the series connection couples the signal output (13) to the signal input (12). A voltage source arrangement (19) of the sensor arrangement (10) is connected to a feedback node (18) between the capacitive sensor (14) and the feedback capacitor (15).