Patent ID: 8093886
Filing Date: 2012-01-10
Classification: G01D

Abstract:
1. A rotation-angle-detecting apparatus comprising a magnet rotor, a magnetic sensor detecting the direction of magnetic flux from said magnet rotor, a correction circuit, and an angle-calculating circuit, said magnetic sensor having a bridge circuit X comprising four connected magnetoresistive devices and a bridge circuit Y comprising four connected magnetoresistive devices, each of said magnetoresistive devices comprising a spin-valve, giant-magnetoresistive film comprising a pinned layer having a magnetization direction fixed in one direction, a free layer whose magnetization direction is variable to be in alignment with the direction of an external magnetic field, and an intermediate layer sandwiched by said pinned layer and said free layer, said correction circuit calculating difference (Vx−Vy) and sum (Vx+Vy) from the output voltage Vx of said bridge circuit X and the output voltage Vy of said bridge circuit Y, and making their amplitudes equal to each other, and said angle-calculating circuit conducting the arctangent calculation of (Vx−Vy)′/(Vx+Vy)′ obtained from a signal (Vx−Vy)′ and a signal (Vx+Vy)′ supplied with the same amplitude from said correction circuit, to determine the rotation angle of said magnet rotor.