| 摘要 |
PURPOSE:To improve the linearity of an output digital signal by feeding back a DC level of a video signal inputted to two A/D converting circuits via a differential amplifier to which a reference voltage is applied. CONSTITUTION:Video signals (b, a) different in polarity and DC component from each other are fed to A/D converters 14, 15 from two amplifier circuits 13, 12. The DC level difference between the converters 14, 15 is biased by connecting an effective range of the converter 14 and the effective range of the converter 15 accurately. In adding input signals to the converters 14, 15, since the polarity of the video signals (a, b) is inverted, only the DC component is left. The difference between the DC component and the reference voltage of a reference voltage source 18 is amplified, fed back to the amplifier circuit 13 to stabilize the DC level of the input signal to the A/D converter 14. Digital data from the converters 14, 15 are composed by an operation circuit 16 and a digital data having 1 bit more than the quantized bit number of the converters 14, 15 is outputted.
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