The speed detection circuit selects the A44E Hall sensor. According to the Hall effect, an element made of semiconductor materials is called a Hall element. It has the advantages of sensitivity to magnetic field, simple structure, small size, wide frequency response, large output voltage change and long service life. Therefore, it has been widely used in the fields of measurement, automation, computer and information technology. Since the potential difference generated by the Hall element is very small, the Hall element, amplifier circuit, temperature compensation circuit, and stabilized power supply circuit are usually integrated on a chip, called A44E Hall sensor.