Patent ID: 7659716

Claim:
A sensor circuit comprising: a sensor portion arranged to obtain, as an electrical signal, information regarding an object to be measured or detected; and a control circuit arranged to control an operation of the sensor portion, wherein the control circuit is arranged to receive a start input signal inputted thereto from outside for making the sensor portion operate only for a given duration after the start input signal is inputted thereto, and wherein the sensor portion includes: a magnetoelectric conversion element arranged to produce, at a first terminal pair or a second terminal pair thereof, an output voltage commensurate with magnetism applied thereto; a switching circuit arranged to switch between a first switching state, in which a power supply voltage is applied to the first terminal pair and an output voltage appearing at the second terminal pair is outputted between a first output node and a second output node, and a second switching state, in which the power supply voltage is applied to the second terminal pair and an output voltage appearing at the first terminal pair is outputted between the first output node and the second output node; an amplifying unit arranged to output, to a first amplification output node, a first amplified voltage obtained by amplifying a first input voltage at the first output node, the first input voltage being inputted to a first amplification input node, by a predetermined amplification factor, the amplifying unit further arranged to output, to a second amplification output node, a second amplified voltage obtained by amplifying a second input voltage at the second output node, the second input voltage being inputted to a second amplification input node, by the predetermined amplification factor; a comparing unit arranged to compare a first comparison voltage inputted to a first comparison input node with a second comparison voltage inputted to a second comparison input node, the comparing unit further arranged to produce a comparison output when the first comparison voltage is higher than the second comparison voltage; a first capacitor between the first amplification output node and the first comparison input node; a second capacitor between the second amplification output node and the second comparison input node; a first switch circuit arranged to apply a first reference voltage to the first comparison input node in the first switching state; a second switch circuit arranged to apply a second reference voltage to the second comparison input node in the first switching state; and a latch circuit arranged to latch the comparison output from the comparing unit and to output an output signal of the sensor portion.