Patent ID: 6392407
Filing Date: 2002-05-21
Classification: G01D

Abstract:
A rotation angle detecting device comprising:a bridge circuit in which while a magnetic field applied to a magnetic detecting element is changed by rotating a magnetic rotation member mounted on a predetermined rotation shaft, said magnetic field change is converted into a voltage change; a first differential amplifying circuit for amplifying the signal outputted from said bridge circuit; an AC (alternating current) coupling circuit for removing a DC component from the output signal of said first differential amplifying circuit; a second differential amplifying circuit for amplifying the signal output from the AC coupling circuit; a comparing circuit for comparing the signal outputted from said second differential amplifying circuit with a predetermined reference value to thereby output any one of a signal of â€œ0â€  and a signal of â€œ1â€ ; an output circuit for waveform-shaping said signal having â€œ0â€ , or â€œ1â€  outputted from said comparing circuit; and an initiating circuit including a first transistor, a second transistor, a third transistor, and a differentiating circuit for driving said first to third transistors; in which both said first transistor and said second transistor are connected to said AC coupling circuit so as to converge the output signal of said AC coupling circuit into a reference voltage immediately after a power supply is turned ON; and in which said third transistor is connected to said comparing circuit so as to also converge the input signal of said comparing circuit into an AC coupling reference level.