Patent ID: 8378674

Claim:
A magnetic field detection device, comprising: a substrate; at least one magneto-resistance element provided on one main surface of said substrate; at least one on-substrate magnetic body which is provided on said one main surface or another main surface of said substrate to be on and fully supported by said one main surface or another main surface of said substrate, and is electrically insulated from said magneto-resistance element; and an external magnetic circuit which is provided on an entering portion side of said on-substrate magnetic body, on which a magnetic field enters, and is magnetically coupled with said on-substrate magnetic body, and guides said magnetic field to said on-substrate magnetic body; wherein: said external magnetic circuit includes an externally-mounted magnetic body which is magnetically coupled to said main surface serving as said entering portion of said on-substrate magnetic body; said externally-mounted magnetic body is disposed in proximity to a generation source of said magnetic field so that said magnetic field is guided to said entering portion through said externally-mounted magnetic body; said generation source of said magnetic field comprises magnetic poles of a rotor whose side surfaces are alternately magnetized into a north pole and a south pole; said externally-mounted magnetic body is disposed on said on-substrate magnetic body so as to extend in parallel with a rotation axis of said rotor; said at least one magneto-resistance element includes a plurality of magneto-resistance elements; and said plurality of magneto-resistance elements are arranged so that a magnetization direction of a fixed layer is substantially perpendicular to said rotation axis of said rotor.