Patent ID: 8283919
Filing Date: 2012-10-09
Classification: G01R

Abstract:
1. A magnetic sensor that detects intensity of a magnetic field and compares a result of the detection with a set threshold value to provide an output signal according to the result of the comparison, the magnetic sensor comprising: a threshold-value adjuster adapted to adjust the threshold value; a magnetoelectric conversion element adapted to produce across a first pair of terminals or across a second pair of terminals an output voltage according to magnetism applied thereto; a switch circuit adapted to be switched between a first switching state in which the switch circuit applies a source voltage across the first pair of terminals and outputs the output voltage appearing across the second pair of terminals between first and second output terminals and a second switching state in which the switch circuit applies the source voltage across the second pair of terminals and outputs the output voltage appearing across the first pair of terminals between the first and second output terminals; an amplifier unit adapted to output to a first amplification output terminal a first amplification voltage obtained by amplifying at a predetermined amplification factor the voltage at the first output terminal received at a first amplification input terminal and to output to a second amplification output terminal a second amplification voltage obtained by amplifying at the predetermined amplification factor the voltage at the second output terminal received at a second amplification input terminal; a comparison unit adapted to compare a first comparison voltage fed to a first comparison input terminal with a second comparison voltage fed to a second comparison input terminal and to produce a comparison output when the first comparison voltage is higher than the second comparison voltage; a first switch circuit adapted to apply a first reference voltage or a corrected first reference voltage to the first comparison input terminal when the switch circuit is in the first switching state; and a second switch circuit adapted to apply a second reference voltage to the second comparison input terminal when the switch circuit is in the first switching state, wherein the amplifier unit includes: an output terminal of the first operational amplifier is connected to the first amplification output terminal and to one end of the first variable resistor, another end of the first variable resistor is connected to an inverting input terminal of the first operational amplifier and to one end of the first resistor, a third reference voltage is fed to another end of the first resistor, a non-inverting input terminal of the first operational amplifier is connected to the first output terminal, an output terminal of the second operational amplifier is connected to the second amplification output terminal and to one end of the second variable resistor, another end of the second variable resistor is connected to an inverting input terminal of the second operational amplifier and to one end of the second resistor, the third reference voltage is fed to another end of the second resistor, a non-inverting input terminal of the second operational amplifier is connected to the second output terminal, and the threshold value adjuster includes the first and second variable resistors.