US Patent 7425821 Chopped Hall effect sensor

A chopped Hall effect sensor topology includes a switched Hall plate, an amplifier responsive to an output of the switched Hall plate and a filter stage responsive to the output of the amplifier and including an anti-aliasing filter and a selective filter that is tuned to the modulation frequency. The switched Hall plate includes a Hall element and a Hall plate modulation circuit that modulates the Hall offset signal component or the magnetic signal component. In embodiments in which the Hall offset signal component is modulated by the switched Hall plate, the amplifier, if chopped, includes an even number of additional modulation circuits. In embodiments in which the magnetic signal component is modulated by the switched Hall plate, the amplifier contains an odd number of modulation circuits. The described topology provides a low noise, fast response time Hall effect sensor.