| 摘要 |
PURPOSE:To remove a DC component at a stage of comparison and to eliminate the influence of variation in DC component by adding the DC component to the reference voltage of a comparator. CONSTITUTION:When a hold signal Sb is supplied to a sample holding circuit 1, the current level of a video signal Sa is held by the sample holding circuit 1, whose output signal Sc is set to a voltage Ca and added to an offset voltage DELTAV by an adder 5, thereby outputting a signal Se. Consequently, a voltage Va+ DELTAV is impressed to the upper end 7 of a resistance network 4 and the voltage Va is impressed to the lower end 6. The video signal is in such form that an AC component is superposed upon a pedestal signal Sc, so they cancel one another at comparators C1-Cn, which compare the AC component of the video signal Sa with voltages DELTAV/(n+1), 2.DELTAV/(n+1), 3.DELTAV/(n+1)-, thereby removing the influence of the pedestal signal Sc. |
