Magnetic-field-angle measurement apparatus and rotational-angle measurement apparatus using same

摘要

In a magnetic-field angle detection device and a rotation angle detection device in which the accuracy of the measured angle is not degraded even if the MR ratio of the tunneling magnetoresistance element is increased. In a magnetic-field-angle measurement apparatus including a magnetic-field-angle detection circuit and a magnetic sensor having a tunneling magnetoresistance element with a pinned magnetic layer, the magnetic-field-angle detection circuit has a power-supply unit that outputs a constant voltage as a bias voltage to the tunneling magnetoresistance element of the magnetic sensor and a current-detection unit that detects an output current of the tunneling magnetoresistance element. The accuracy of the measured angle of the magnetic-field angle detection device and the rotation angle detection device is improved by measuring the tunneling magnetoresistance element current while maintaining the terminal voltage of the tunneling magnetoresistance element constant with input impedance of the current-detection unit as zero.

主权项

1. A magnetic-field-angle measurement apparatus comprising:
a magnetic sensor; and a magnetic-field-angle detection circuit, wherein the magnetic sensor has a tunneling magnetoresistance element with a pinned magnetic layer, the tunneling magnetoresistance element of the magnetic sensor has first and second feeding terminals and a first sensing terminal, the magnetic-field-angle detection circuit has a power-supply unit that outputs a constant voltage as a bias voltage to the tunneling magnetoresistance element of the magnetic sensor and a current-detection unit that detects a flowing current through the tunneling magnetoresistance element, a terminal voltage of the tunneling magnetoresistance element is detected through the first sensing terminal, and the power-supply unit performs feedback control such that the terminal voltage matches a predetermined voltage value, wherein the power-supply unit has a differential amplifier with differential inputs of an output voltage of the first sensing terminal and an output of a reference-voltage generation unit, wherein the tunneling magnetoresistance element has a second sensing terminal in addition to the first sensing terminal, the second sensing terminal connected to an input terminal of the differential amplifier through the reference-voltage generation unit.