| 摘要 |
PURPOSE:To improve the reliability of the entire circuit, to facilitate the large scale integration of the titled circuit and to attain the miniaturization by fulfilling a clamp function outputting a base level of an input signal while arranging the levels to a constant value digitally at the post-stage of an A/D conversion means. CONSTITUTION:An analog video signal (a) including periodically a base level signal and a sampling clock (b) having a sufficiently high frequency area inputted. The analog video signal (a) are inputted to an A/D converter 3 via a low pass filer 1 and an amplifier 2 and converted into a digital signal synchronously with the clock (b). A digital value Y latched in a latch circuit 5 in a timing is subtracted from a digital value X from a latch circuit 4, generated one after another, in the subtracter 6, and its result of subtraction Z is a coded digital output. Thus, the clamp function is realized while using a digital circuit offering ease of large scale circuit integration mainly to attain the miniaturization.
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