Metal Thin-Film Filter Circuit for Low 1/f Noise Stability
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Solution Overview
Problem
Existing circuit devices, such as those used in gyro sensors, suffer from long-term stability issues due to increased 1/f noise, which is not effectively reduced by Allan variance for long time intervals, affecting the accuracy of physical quantity measurements.
Innovation Solution
A circuit device incorporating a filter circuit with a metal thin film layer, formed on a non-doped polysilicon substrate with an insulating film, and an A/D conversion circuit to reduce noise, specifically using a silicide layer as the metal thin film, which reduces 1/f noise and enhances long-term stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a polysilicon resistor is used in the amplification circuit, then the circuit can be manufactured with standard semiconductor processes, but the 1/f noise is increased and long-term stability deteriorates
Solution Approach 1:
The patent changes the material parameter of the resistor from polysilicon to metal thin film, fundamentally altering the resistance implementation to reduce 1/f noise while maintaining manufacturability through standard thin film deposition processes
Solution Approach 2:
The patent employs a composite structure with multiple metal layers (first metal layer and second metal layer with different resistivities) to achieve optimal noise performance and electrical characteristics while maintaining ease of manufacture through layered material composition
2Reliability
If a filter circuit with metal thin film layer is used, then the 1/f noise is reduced and long-term stability is improved, but the device structure becomes more complex
Solution Approach 1:
The patent merges the filter circuit and amplification circuit into a single integrated device, combining multiple functions (filtering, amplification, temperature compensation) into one unified structure to reduce overall system complexity while maintaining improved long-term stability
Solution Approach 2:
The metal thin film resistor serves multiple functions simultaneously: it acts as both the filtering element and the amplification circuit resistor, while also providing temperature compensation characteristics, thereby reducing the need for separate components and simplifying the overall device structure
Data Source
AI summary
A circuit device includes a filter circuit to which a detection signal is input and which has a resistance element including a metal thin film layer, and an A/D conversion circuit performs A/D conversion of the detection signal filtered by the filter circuit and outputs detection data.