| 摘要 |
PURPOSE:To prevent an error of signal detection at the post-stage by providing a peak detection circuit of an input signal voltage, a voltage-current conversion circuit, a full-wave rectifier circuit and a comparator and detecting a peak value and a reference value to set a voltage DELTAV thereby decreasing the deviation of the timing due to the fluctuation of the peak value. CONSTITUTION:The value DELTAV is selected by the resistance voltage division by the peak value and the reference value so that no deviation of the detection timing is caused because of the fluctuation of the peak value of the input voltage. In applying the input voltage waveform to an input A or B being in the opposite phase relation, a waveform whose peak value is subjected to holding appears at the emitter of a transistor (TR) Q7. The voltage difference Vp between the peak voltage and the reference voltage is converted into a current by a voltage-current conversion circuit 2. In such a case, the current flowing to a collector of a TR Q14 is 2Vp/R4 and the value DELTAV is set by a value of 2Vp.R1/R4. Thus, even if the peak value of the input voltage is fluctuated, its peak value is detected and converted into a current to set the value DELTAV depending on the ratio of the resistances R1, R4 in an IC.
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