DRIVE CIRCUIT FOR MAGNETIC IMPEDANCE EFFECT ELEMENT

PROBLEM TO BE SOLVED: To dispense with adjustment of characteristics of an excitation coil and to reduce size and weight by applying a bias magnetic field to a plurality of MI elements by the single excitation coil energized by a current with its direction reversed alternately. SOLUTION: Linear magnetic bodies 1a, 1b are surrounded by a single excitation coil 2 having tens of turns wound in a fixed direction for applying thereto a direct-current bias magnetic field. That is, the linear magnetic bodies 1a, 1b are disposed at a core part of the excitation coil 2. First and second element drive circuits 6a, 6b pass pulse-train currents through the first and second linear magnetic bodies 1a, 1b, respectively. A coil drive circuit 7 equipped with a switching element for on/off controlling the energization of the excitation coil 2, acts to periodically reverse the direction of the bias magnetic field generated by the excitation coil 2. A detection circuit 8 has first and second smoothing parts 9a, 9b, and output signals from the two are inputted into and differentially amplified by an operational amplifier 10. Thus, only one excitation coil 2 is enough for applying the bias magnetic field to the magnetic impedance effect elements (MI elements).