| 摘要 |
PURPOSE:To obtain a separating circuit for vertical synchronizing signal which has high resistance to noise, weak electric field and field variance, by securing AC coupling via a capacitor between an integrator to which a composite synchronizing signal is supplied and a non-reverse amplifier which delivers a vertical synchronizing signal. CONSTITUTION:When a composite synchronizing signal is supplied to an input terminal 11, the vertical synchronizing signal is separated from the composite synchronizing signal by an integrator 12. This separated synchronizing signal is amplified by a non-reverse amplifier 14 which is AC-coupled to a coupling capacitor 13 and outputted through an output terminal 15. The synchronizing signal supplied to the amplifier 14 is amplified based on zero volt. Thus the level of noises produced at the amplifier the amplifier 14 and the level fluctuation due to a weak electric field, etc. can be reduced. Therefore, only the normal synchronizing signal can be extracted by a digital circuit by setting the threshold value of a digital circuit connected to the terminal 15 at a level higher than said level fluctuation.
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