| 摘要 |
PURPOSE:To establish a point of time of generation of a pulse electromotive force with high accuracy independently of the level of a maximum peak of an AC input signal by generating a pulse electromotive force from a detection coil being a magnetism sensing element at a zero cross point of the AC output when the AC output of an operational amplifier is fed to an exciting coil of the magnetism sensing element generating the pulse electromotive force in response to the change in an external magnetic field. CONSTITUTION:Since a differential output of an operational amplifier 1 with an AC input signal Vs and a DC control signal Vd fed respectively to input terminals S, D has a waveform shifting a ground line G of the signal Vs toward a line Go and a point of time of a phase (x) in the AC input signal is a zero cross point between the differential output current and the Go, the pulse electromotive force E is induced at this point of time. In this case, since the point (x), that is, the zero cross point of the differential output is controlled properly to a desired point of time by varying the level of a DC control signal Vd, the pulse electromotive force is induced accurately at a required point of time. Then in applying the pulse electromotive force E to a gate of a semiconductor control element 5, such as a thyristor, the operation of a circuit 6 to be controlled is controlled at a proper timing as the trigger signal.
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