A magnetic field-induced current-modulating opamp based on CMOS differential Tesla-Volt multiplier cell for MAGFET 1/f noise reduction

A magnetic field-induced current-modulating opamp (MCMOP) based on the CMOS differential Tesla-Volt multiplier (TVM) cell for magnetic field-effect transistor (MAGFET) 1/f noise reduction is reported. It consists of a CMOS differential TVM cell made of a pair of identical MAGFETs, a fully differential opamp, and a set of chopper-stabilization switches. Due to the modulation effect of the input voltage on the magnetic field-induced current imbalance, the MCMOP is utilized as a linear magnetic sensor not only to amplify the magnetic signal, but also to chop and stabilize the signal, so as to suppress the low frequency noise in the MAGFETs themselves. By introducing the MCMOP, the magnetic noise level of the magneto-opamp (MOP) consisting of the same differential opamp and the same single MAGFET is reduced from 160 to 25 μT/Hz1/2 at 1 Hz. This is a 16 dB improvement of the magnetic resolution.