Magnetic field detection sensor

A magnetic field detection sensor comprising:

• a magneto-impedance element configured to make use of a magneto-impedance effect;
• a bias coil configured to apply a bias magnetic field to the magneto-impedance element;
• an oscillator circuit configured to apply an alternating-current to the magneto-impedance element;
• a differentiating circuit configured to differentiate an output of the magneto-impedance element;
• a flip-flop circuit configured to output a high level signal and a low level signal based on a trigger waveform output from the differentiating circuit;
• and
• a computing unit configured to detect an external magnetic field based on a high and low timing of the high level and low level signal output from the flip-flop circuit, wherein
• the magnetic field detection sensor is configured to detect the external magnetic field based on an output obtained by applying the alternating-current to the magneto-impedance element,
• the magneto-impedance element includes a non-magnetic substrate and a magnetic film provided on a surface of the non-magnetic substrate, a magnetic field detecting direction matches a longitudinal direction of the magneto-impedance element, and the magnetic film is configured to have a magnetic anisotropy such that an axis of easy magnetization thereof matches the magnetic field detecting direction, and
• the computing unit is configured to transmit a reset signal to the flip flop circuit at timing of a fall of an alternating-current bias frequency, and detect the external magnetic field based on a duration of a first negative-side of the trigger waveform subsequent to the reset signal.