| 摘要 |
A rotation detecting device includes a rotary member having teeth, a biasing magnet, a magnetic sensor unit and a differential amplifier circuit for providing an output signal Vd. The sensor unit includes four bridge circuits of magnetoresistive elements that provide voltage signals V 1 , V 2 , V 3 , V 4 . The differential amplifier circuit includes a first differential amplifier for providing a first signal that is a difference between the voltage signals V 1 , V 2 , a second differential amplifier for providing a second signal that is a difference between the voltage signals V 3 , V 4 , a first circuit for providing a first amplified signal of the first signal amplified by a variable gain alpha, second circuit for providing a second amplified signal of the second signal amplified by a fixed gain and a third differential amplifier for providing the output signal Vd by a difference between the first amplified signal and the second amplified signal. The variable gain is adjusted to provide a minimum air-gap characteristic point that corresponds to a fixed rotation angle relative to the teeth.
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