| 摘要 |
PURPOSE: To solve the problem that a circuit scale has been large since an activation circuit has been using an operational amplifier conventionally. CONSTITUTION: The rotary angle detector comprises a bridge circuit 10 for converting the magnetic field change in an MR element 5 to a voltage change, a differential amplification circuit 20 for amplifying the output of the bridge circuit, an AC coupling circuit 30 for removing the DC component in the output of the differential amplification circuit 20, a differential amplification circuit 40 for amplifying the output of the AC coupling circuit, a comparison circuit 50 for comparing the output of the differential amplification circuit 40 with a reference value for outputting 0 and 1 signals, an output circuit 60 for shaping the waveform of the output in the comparison circuit, transistors 75, 76, and 74, and a differential circuit 71 for driving them. In addition, the rotary angle detector has an activation circuit 70A for connecting the transistor 75 and 76 to the AC coupling circuit, converges the output signal to a reference voltage immediately after power is turned on, and connects the transistor 74 to the comparison circuit for also converging the input signal of the comparison circuit to the AC coupling reference level, thus reducing the circuit scale and hence reducing costs.
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