| 摘要 |
PURPOSE:To detect a zero cross point stably and at a high speed by a simple constitution by logically processing outputs of comparators set to different levels for comparison of input signals. CONSTITUTION:Set levels of comparators 31 and 32 are set to a level and zero-cross level higher than those of noises of an approximately zero cross level. When strobe signal ST becomes high in level, an output of comparator 32 having passed through comparator 31 and inverter 37 with NAND gates 33 and 34 open is applied to FF and when FF is set by the output of comparator 31, the following output of comparator 32 is outputted as a zero cross signal. Therefore a zero cross point can be detected stably and at high speed through the temperature-compensation of only the set level applied to comparators by the simple constitution using no tunnel diode, etc.
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