An integrated CMOS micro search‑coil magnetometer with on‑chip calibration and a low‑noise amplifier

Area of Science:

• Integrated circuit design
• Magnetic field sensing technologies
• Low-power electronics

Background:

• Traditional search-coil magnetometers (SCMs) face limitations in power consumption and integration.
• Existing CMOS SCMs require further optimization for noise performance and energy efficiency.

Purpose of the Study:

• To develop a fully CMOS-integrated micro search-coil magnetometer (µSCM) with enhanced performance.
• To achieve a significant reduction in noise equivalent magnetic induction (NEMI) and power consumption.
• To optimize the µSCM for a wide frequency range (1 Hz to 1 kHz).

Main Methods:

• Implementation in a standard TSMC 180 nm CMOS process utilizing an Integrated-within-Aperture layout.
• Integration of a low-noise instrumentation amplifier (INA) with a nested-chopped current-feedback architecture.
• Application of a theoretical framework to optimize inductor geometry (line width wc, inner diameter Dic) for minimal NEMI.

Main Results:

• Achieved a noise equivalent magnetic induction (NEMI) of 2.1 nT/√Hz at 1 kHz.
• Demonstrated ultra-low power consumption of 364 µW, a tenfold improvement over prior CMOS SCMs.
• Reduced input-referred noise of the integrated INA from 73.45 nV/√Hz to 36.92 nV/√Hz at 100 Hz.

Conclusions:

• The developed µSCM represents a significant advancement in integrated magnetic sensing.
• Its compact size, high efficiency, and low noise make it suitable for demanding applications.
• Potential applications include biomedical diagnostics, environmental monitoring, and energy-efficient systems.