| 摘要 |
PURPOSE:To remove an unnecessary signal by comparing a reference voltage responded and generated to an initial code pulse and a pulse column signal after the initial code pulse. CONSTITUTION:An initial code selecting gate generating circuit 2b generates a holding gate signal equivalent to the code pulse for one period confirmed by an initial code selecting circuit 2a and outputs it to a reference voltage generating circuit 3. A gate switch circuit 3c prohibits that a pulse column signal is outputted to a charging/discharging circuit 3d while the holding gate signal exists. Thus, the voltage of the charging/discharging circuit 3d is held by the initial pulse column received immediately before the holding gate signal occurs. Consequently, to the code pulse in the same period received thereafter, the amplitude level of the level or above to which a level comparator 1d is set does not exist and only then, the output of a comparator 1b does not appear. Thus, the unnecessary signal can be removed.
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