DC Clamp Amplifier Circuit for Low-Frequency Magnetic Signal Detection
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Solution Overview
Problem
Existing magnetic sensor devices require large amplification gains to detect low-frequency magnetic patterns, leading to amplifier saturation and incorrect waveform detection due to fluctuations in resistance elements, power source voltage, and temperature, which results in increased device size and complexity.
Innovation Solution
The proposed solution involves a compact amplifier design using a DC clamp amp or DC clamp servo amp configuration with operational amplifiers, capacitors, and switches, which allows for precise control of the midpoint voltage and phase margin, enabling efficient amplification of low-frequency components while minimizing device size and power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If large gain amplification is applied to amplify the low midpoint voltage, then the detection sensitivity is improved, but amplifier saturation occurs and correct waveform detection becomes impossible
Solution Approach 1:
The patent applies preliminary action by removing the direct-current component from the detected signal before amplification. This is achieved through a high-pass filter that eliminates the DC portion of the signal, allowing subsequent amplification to focus only on the AC component containing the magnetic pattern information. This prevents amplifier saturation while maintaining detection sensitivity.
Solution Approach 2:
The patent extracts and removes the direct-current component from the detected signal using a high-pass filter. By separating and eliminating the DC portion, the system amplifies only the relevant AC signal containing magnetic pattern data, avoiding saturation issues while preserving measurement precision.
2Reliability
If high-pass filter with large electrostatic capacitance is used to remove direct-current signal, then the DC component is effectively removed, but the signal processing circuit becomes larger
Solution Approach 1:
The patent changes the parameter of electrostatic capacitance from large (μF order) to small (pF order) by modifying the cutoff frequency of the high-pass filter. This is achieved by carefully selecting the resistance and capacitance values in the filter circuit, allowing effective DC removal with minimal circuit size increase.
Solution Approach 2:
The patent applies local quality by using a small capacitance value (pF order) specifically in the high-pass filter circuit where it is most effective. This localized optimization allows DC removal without requiring large capacitors throughout the entire signal processing chain, thus minimizing overall circuit size.
3Reliability
If only changed portion is amplified omitting direct-current portion, then amplifier saturation is avoided, but low-frequency components may be lost
Solution Approach 1:
The patent applies dynamics by using a high-pass filter with an appropriately selected cutoff frequency that dynamically passes low-frequency AC components while blocking DC. The filter's frequency response is designed to maintain stability in amplifier operation while preserving low-frequency magnetic pattern information, avoiding the loss of valid signals.
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 approach reduces the size and power consumption of the amplifier and signal processing device while effectively amplifying low-frequency components, stabilizing the midpoint voltage, and improving signal-to-noise ratio, thereby enhancing the accuracy of magnetic sensor detection.
Implementation Method 1
a magnetic sensor device for detecting magnetic patterns in a detectable body using a magnetic resistance effect element having the property that the resistance value changes under an impressed magnetic field
Implementation Method 2
a capacitor (C1) having a small electrostatic capacitance of several tens of pF
Data Source
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AI summary
When a switch (SW1) is set to off, and a switch (SW2) is set to on, the voltage of a SigOut terminal (205) is stabilized with a reference voltage, and a bias voltage is applied to a capacitor (C1). Changing the switch (SW2) from on to off, with the bias voltage retained in the capacitor (C1), a detection signal which is input via a SigIn terminal (201) is amplified with the reference voltage as a reference, and an amplified signal is output from the SigOut terminal (205).