MagFET Spinning Current Biasing Circuit Offset Error Reduction
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Solution Overview
Problem
Magnetic field sensors, particularly MagFETs, face challenges in accurately measuring magnetic fields due to asymmetries and variations in sensor layouts, leading to offset errors in voltage measurements.
Innovation Solution
A method for operating MagFETs involves alternately configuring the biasing circuit to switch between two operating modes, combining output voltages to reduce offset errors, and maintaining constant gate-bulk and drain-gate voltages across modes, utilizing electronic switches and specific terminal configurations to achieve rotational symmetry and improve measurement accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a MagFET sensor uses a fixed biasing circuit configuration, then the device structure is simple, but offset errors occur due to asymmetries and layout variations
Solution Approach 1:
The biasing circuit is made reconfigurable by alternating between first and second configurations. Electronic switches enable dynamic switching between different circuit topologies, allowing the sensor to operate in multiple modes that compensate for asymmetries and reduce offset errors through differential measurement techniques.
Solution Approach 2:
The biasing circuit periodically alternates between first and second configurations in a spinning current scheme. This periodic switching enables time-multiplexed measurement modes where output voltages are tapped at different phases, allowing offset cancellation through combination of measurements taken in different operational states.
2Measurement precision
If the biasing circuit is reconfigured to reduce offset errors, then measurement accuracy improves, but the switching between operating modes increases complexity
Solution Approach 1:
The biasing circuit is designed with multi-functionality to perform both sensing and offset cancellation operations. The same circuit components and electronic switches serve dual purposes: establishing operational modes for measurement and simultaneously enabling offset error compensation through configuration switching, reducing the need for separate dedicated components.
Solution Approach 2:
The offset compensation mechanism is merged with the operational biasing circuit rather than being a separate system. The electronic switches that reconfigure the biasing circuit are integrated into the same circuitry used for sensing, combining the functions of mode switching and offset cancellation into a unified system that reduces overall device complexity.
3Reliability
If multiple operating modes are used to compensate for asymmetries, then measurement reliability improves, but the operation and control of the sensor becomes more complex
Solution Approach 1:
The sensor system performs self-diagnosis and self-compensation by automatically alternating between operating modes and combining output voltages to cancel offset errors. The evaluation circuit automatically processes the tapped voltages from different modes to produce a corrected measurement, eliminating the need for manual calibration or complex external control mechanisms.
Solution Approach 2:
The system uses feedback through the evaluation circuit that combines output voltages from multiple operating modes. The combination process provides automatic feedback on the measured values, allowing the system to identify and compensate for offset errors by comparing measurements taken in different configurations, thereby improving reliability without requiring complex external control.
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 enhances the accuracy of magnetic field measurements by minimizing offset errors caused by asymmetries and layout variations, providing a more reliable and precise method for detecting magnetic fields.
Implementation Method 1
The gate electrode is separated from the first well region by an isolation layer and is configured to control a charge carrier density in the first well region between the contact regions dependent on a voltage applied at the gate electrode
Implementation Method 2
A magnetic field sensitive MOSFET (usually referred to as MagFET) is a magnetic field sensor, which makes use of the deflection of the current passing through the MOS channel of a MagFET caused by a magnetic field. This deflection is caused by the Lorentz force acting on the charge carriers in the MOS channel
Data Source
AI summary
A magnetic-field-sensitive MOSFET (MagFET) is described herein. In accordance with one embodiment, the MagFET comprises a semiconductor body, a first well region arranged in the semiconductor body and being doped with dopants of a first doping type, and a number of N contact regions arranged in the first well region and doped with dopants of a second doping type, which is complementary to the first doping type, wherein N is equal to or greater than three. A gate electrode covers the first well region between the contact regions. The gate electrode is separated from the first well region by an isolation layer and is configured to control a charge carrier density in the first well region between the contact regions dependent on a voltage applied at the gate electrode. The first well region has a center of symmetry and the contact regions are arranged rotationally symmetric with respect to the center of symmetry with a rotational symmetry of order N.