Comments on “A CMOS Front-End Hall Sensor Microsystem for Linear Magnetic Field Measurement With Best Tradeoff Between Sensitivity and SNR”

In the above article (Xu et al., 2022), it is claimed that the sensitivity of the output signal of a Hall-plate with respect to an applied magnetic field is doubled when the Hall-plate is operated in current mode instead of traditional voltage mode. The proof was based on a Wheatstone bridge model where two resistors increase with the magnetic field while the other two resistors decrease. However, a resistor network with magnetic field-dependent resistors can only describe the magneto-resistance effect of a Hall-plate, yet it cannot describe the Hall-effect of a Hall-plate. A correct representation of a Hall-plate is given by a resistor network and controlled voltage or current sources, or gyrators. The application of this correct network shows that neither the sensitivity of the output signal nor the signal-to-thermal-noise ratio (SNR) differ in current and voltage modes. It also shows that the proposed spinning current scheme does not perfectly eliminate offset errors of the Hall-plate.