Frequency-modulation-type MI sensor using amorphous wire and CMOS inverter multivibrator

A new frequency-modulation-type magnetoimpedance (MI) sensor using amorphous wire and a complimentary metal-oxide-semiconductor (CMOS) multivibrator is presented. The normal switching mode (mode I) with the alternative saturation and off states in the p-MOSFET and n-MOSFET maintains a stable multivibrator oscillation and simultaneous CMOS unsaturation state mode (mode II) generates a sensitive MI effect. A 50%/Oe change in the oscillation frequency versus external dc magnetic field was obtained. A linear sensor characteristic is obtained using a negative feedback through a frequency-voltage converter.