| 摘要 |
PURPOSE:To attain highly stable A/D conversion by utilizing a difference be tween a black level of a digital output signal from the A/D converter and a preset level to improve the stability against temperature change and external noise. CONSTITUTION:An analog video signal inputted to an input terminal is converted into a digital signal by an A/D converter 3 via a DC component rejection capacitor 2, the signal is fed to an adder 7 and inputted to a black level detector 4. The DC potential output of the black level detector 4 is subtracted from the reference level obtained from a reference level generator 5 by an adder 6 to obtain a difference with the preset level. The difference is added to a digital output signal from the A/D converter 3 by the adder 7 and the result is given to an output terminal 11. |
