Magnetic detection apparatus
View Patent ↗A magnetic detection apparatus is able to make a selection between AC coupling and DC coupling thereby to improve the accuracy of a final output signal corresponding to a magnetic movable element, thus making it possible to ensure excellent detection performance. The magnetic detection apparatus with a sensor composed of magnetoresistive elements ( 2 a , 2 b ) for detecting the strength of a magnetic field includes a first comparison circuit ( 31 ) that has a first comparison level (VR 1 ), and waveform shapes the amplitude of a detection signal (C) from the magnetoresistive elements ( 2 a , 2 b ) through DC coupling, a second comparison circuit ( 32 ) that has a second comparison level (VR 2 ), and waveform shapes the amplitude of the detection signal C through DC coupling, and a third comparison circuit ( 33 ) that has a third comparison level VR 3 , and waveform shapes the amplitude of the detection signal C after AC coupling.
1. A magnetic detection apparatus with a sensor composed of a magnetoelectric conversion element for detecting the strength of a magnetic field, said apparatus comprising:
a first comparison circuit that has a first comparison level, and waveform shapes the amplitude of a detection signal from said magnetoelectric conversion element through DC coupling;
a second comparison circuit that has a second comparison level, and waveform shapes the amplitude of the detection signal from said magnetoelectric conversion element through DC coupling; and
a third comparison circuit that has a third comparison level, and waveform shapes the amplitude of the detection signal from said magnetoelectric conversion element after AC coupling.
2. The magnetic detection apparatus as set forth in claim 1 , wherein said first and second comparison levels are set in such a manner that said third comparison level becomes between said first comparison level and said second comparison level.
3. The magnetic detection apparatus as set forth in claim 1 , further comprising a logical processing circuit that logically processes the respective output signals of said first, second and third comparison circuits.
4. The magnetic detection apparatus as set forth in claim 3 , wherein said logical processing circuit includes:
a second transistor that is turned on and off by an output signal of said first transistor;
a third transistor that is connected in series to said first transistor, and turned on and off by an output signal of said third comparison circuit;
a fourth transistor that is connected in series to said second transistor; and
a fifth transistor that is turned on and off by an output signal of said second comparison circuit;
wherein said fourth transistor is turned on and off by an output signal of said fifth transistor, and an output signal of said second transistor is made as a final output signal.