Patent ID: 8487612

Claim:
A current sensor comprising: a magnetic detecting bridge circuit formed of four magneto-resistance effect elements with a resistance value varied by application of an induced magnetic field from a current to be measured, the four magneto-resistance effect elements having a same resistance change rate, each of the four magneto-resistance effect elements including: a self-pinned type ferromagnetic fixed layer formed of a first ferromagnetic film and a second ferromagnetic film anti-ferromagnetically coupled to each other; a nonmagnetic intermediate layer; and a soft magnetic free layer; a feedback coil placed in a vicinity of the magneto-resistance effect element, the feedback coil generating a cancelling magnetic field for cancelling the induced magnetic field; and a magnetic shield configured to attenuate the induced magnetic field and to enhance the cancelling magnetic field, wherein the magneto detecting bridge circuit has an output between two of the four magneto-resistance effect elements, magnetization directions of the ferromagnetic fixed layers of the two magneto-resistance effect elements being different from each other by 180°, wherein the magnetic detecting bridge circuit has a wiring symmetrical to a power supply point, and wherein the current to be measured is measured based on a current flowing in the feedback coil at the time of an equilibrium state in which the induced magnetic field and the cancelling magnetic field are cancelled by energizing the feedback coil with a voltage difference obtained from the magnetic detecting bridge circuit.