Patent ID: 7808229

Claim:
A frequency detector comprising: a magnetic device comprising: a magnetoresistive element, wherein a thickness direction of the magnetoresistive element is defined as a Z-axis direction, and two axes orthogonal thereto are defined as an X-axis and a Y-axis, respectively; an upper electrode and a lower electrode being in contact with the two ends in the Z-axis direction of the magnetoresistive element, respectively, and being electrically connected to the magnetoresistive element, wherein the upper electrode and the lower electrode both extend along the Y-axis direction; a magnetic yoke arranged to apply a magnetic field to the magnetoresistive element, and left and right side walls of the magnetic yoke having gradual slopes to form a trapezoidal space in a cross-section of the magnetic yoke to enhance intensity of the magnetic field; a magnetic-field applying interconnection for applying the magnetic field through the magnetic yoke to the magnetoresistive element; wherein the magnetic-field applying interconnection is positioned above the magnetoresistive element via a gap, wherein the magnetic-field applying interconnection extends along the Y-axis and is located in the trapezoidal space between the magnetoresistive element and a top magnet of the magnetic yoke, and the magnetic-field applying interconnection is surrounded by the magnetic yoke; and wherein the upper electrode is located in the trapezoidal space between the magnetoresistive element and the magnetic-field applying interconnection; an input terminal for supplying an alternating-current signal to the magnetoresistive element; an output terminal for extracting an output voltage from the magnetoresistive element; and a current control circuit for controlling an electric direct current flowing through the magnetic-field applying interconnection to sweep the direct current flowing in the magnetic-field applying interconnection; and a monitor circuit for monitoring the voltage outputted from the output terminal, while sweeping the direct current outputted from the current control circuit.