Patent ID: 7800356

Claim:
A position detection apparatus which includes a fixed portion and a movable portion which moves along a plane opposite the fixed portion, a magnet is provided for one of the fixed portion and the movable portion, and a detection unit for detecting a magnetic field generated from the magnet is provided for the other of the fixed portion and the movable portion, wherein: the magnet has a surface to which the detection unit is oppositely disposed, and the surface and a back side portion are magnetized to opposite magnetic poles; the detection unit includes a magnetoresistive effect element which is provided with a fixed magnetic layer having a magnetizing direction fixed, and a free magnetic layer magnetized by the magnetic field applied from the magnet, and has an electric resistance value changed in accordance with a relative angle defined by a fixing magnetizing direction of the fixed magnetic layer and a magnetizing direction of the free magnetic layer so that the fixing magnetizing direction of the fixed magnetic layer is directed along the plane, and a bias magnetic field orthogonal to the plane is applied to the free magnetic layer; and a change in a resistance of the magnetoresistive effect element allows detection of a position of the movable portion in the plane.