Hall Sensor Amplifier Circuit for Stress-Insensitive Sensitivity
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Solution Overview
Problem
Existing semiconductor devices face challenges in reducing stress dependence of physical quantity sensor sensitivity, leading to inaccurate detection due to varying piezoelectric coefficients of resistors, which can result in increased current consumption and unstable operation.
Innovation Solution
A semiconductor device with a voltage divider circuit and transimpedance amplifier configuration, utilizing resistor circuits with different piezoelectric coefficients to minimize stress dependence, while maintaining a small circuit area and low current consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single type of resistor is used in the amplifier circuit, then the circuit structure is simple, but the stress dependence of sensor sensitivity cannot be effectively compensated
Solution Approach 1:
The patent applies local quality by using two different types of resistors (first and second resistors) with different piezoelectric coefficients in specific locations within the amplifier circuit. The first resistor is connected between the output terminal and inverting input terminal, while the second resistor is connected between the non-inverting input terminal and ground. This localized differentiation allows the circuit to compensate for stress-induced sensitivity changes while maintaining overall structural simplicity.
2Measurement precision
If multiple amplifiers are arranged in multiple stages to increase compensation amount, then stress dependence can be reduced, but circuit area and current consumption increase
Solution Approach 1:
The patent changes the parameters of existing circuit elements by selecting resistors with specific piezoelectric coefficients rather than changing the overall circuit architecture. By carefully choosing the resistance values and piezoelectric coefficients of the first and second resistors, the circuit achieves stress dependence compensation within a single amplifier stage, avoiding the need for multiple amplifier stages and thus reducing circuit area.
3Measurement precision
If resistor piezoelectric coefficient is increased to enhance compensation, then stress dependence reduction is improved, but excessive compensation reverses the sign and increases stress dependence
Solution Approach 1:
The patent implements feedback by connecting the first resistor between the output terminal and the inverting input terminal of the amplifier. This feedback mechanism allows the circuit to automatically adjust and balance the stress-induced sensitivity changes. The feedback loop ensures that compensation remains within appropriate limits, preventing excessive compensation that would reverse the sign and destabilize operation.
4Measurement precision
If resistor piezoelectric coefficient is insufficient, then compensation amount is limited, but increasing compensation amount by adding circuit elements increases device complexity
Solution Approach 1:
The patent applies universality by making the amplifier circuit perform multiple functions simultaneously: signal amplification, stress dependence compensation, and automatic balancing. By incorporating the first and second resistors with specific piezoelectric coefficients into the standard amplifier configuration, the circuit achieves stress compensation without requiring separate dedicated compensation circuits, thus avoiding increased device complexity.
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 reduces stress dependence of physical quantity sensor sensitivity, enabling accurate detection with minimal circuit area and current consumption, and suppresses stress dependence coefficients to a tenth of the original value.
Implementation Method 1
a piezoelectric effect occurs due to a mechanical stress (hereinafter simply referred to as 'stress') caused by, for example, a protective film formed on a wafer or resin sealing of a package
Implementation Method 2
a transimpedance amplifier, to which the first current and the second current are to be input in a combined manner, and is configured to output a voltage based on input currents
Data Source
AI summary
The semiconductor device includes a Hall element, a first differential pair, a second differential pair, an output amplifier circuit, and a voltage divider circuit. The Hall element outputs a signal that is dependent on stress to be applied to a semiconductor substrate to the first differential pair. The voltage divider circuit divides a voltage into a divided voltage having a voltage dividing ratio that is dependent on the stress. The first differential pair outputs a first current based on the signal. The second differential pair outputs a second current based on the divided voltage and a reference voltage. The output amplifier circuit outputs a voltage based on the first and second currents. A gain of the output amplifier circuit is approximated by a sum of a difference between stress dependence coefficients of transconductances of the first and second differential pairs and a stress dependence coefficient of the voltage dividing ratio.