| 摘要 |
PURPOSE:To detect a static magnetic field or a magnetic field in a low frequency area at a high accuracy irrelevant to temperature changes by processing output of an AC amplifier for amplifying output of a magnetoresistance effect element (MR element) synchronizing changes in a bias magnetic field. CONSTITUTION:A square wave current equal in the positive and negative absolute value is applied to a bias wire 3 near an MR element 2 from a bias current source 1. The sum of a signal magnetic field S and a bias magnetic field B, the magnetic field S+B is applied to the MR element 2. As a voltage opposite in the polarity at an output terminal (a) is outputted to an output terminal (b) of an AC amplifier 5, an output voltage of a switch 6 to be operated at the same timing as the bias magnetic field shifts to one side so that the output of a low pass filter 7 will turn to a DC output according to the signal magnetic field S clear of a high frequency component. The output will not be affected by the offset of the temperature changes developing as DC component thereby enabling the detection of a magnetic field at a high accuracy without requiring any temperature compensator. |
