Patent ID: 7205761

Claim:
A rotation state detecting device, comprising: a magnet creating a bias field; first and second bridge circuits disposed in the bias field of the magnet and facing a pronged magnetic rotating body constituting a detection object side by side in the rotation direction thereof, made up of magneto-resistance effect elements that undergo resistance changes caused by state changes of the bias field corresponding to rotation of the detection object; a first comparator for detecting an increasing/decreasing direction of the center point voltage of the first bridge circuit ( 11 ) and outputting a corresponding logic value; a second comparator for detecting an increasing/decreasing direction of the center point voltage of the second bridge circuit and outputting a corresponding logic value; a third comparator for detecting a difference between the center point voltage of the first bridge circuit and the center point voltage of the second bridge circuit and outputting a corresponding logic value; and logic value information deriving means for outputting “1” when the logic values of the outputs of the first comparator and the second comparator are both “1”, outputting “0” when they are both “0”, and continuing to output the previous value at other times, wherein the direction of rotation of the detection object is determined on the basis of a combination of the outputs of the first, second and third comparators and the logic value information deriving means.