| 摘要 |
<p>PURPOSE:To obtain the A/D converter for video signal controlling a level of the video signal having two different blanking levels accurately. CONSTITUTION:A clamp circuit 10 clamps a blanking level of a color difference signal C by a voltage level V2 being a half of a reference voltage and an A/D converter circuit 11 is used to convert the clamped level into a digital signal. A level error detection circuit 12 calculates an error in a blanking level of a luminance signal Y with respect to a reference value and an integration circuit 15 integrates the error and the integrated signal is converted into an analog signal by a D/A converter 16 and a reference voltage generating circuit 17 generates a reference voltage level V1 based on the analog signal. The A/D converter circuit 11 uses the reference voltage level V1 to apply A/D-conversion to the voltage and applies a voltage level V2 being a half of the reference voltage to the clamp circuit 10. Thus, the blanking level of both the color difference signal C and the luminance signal Y is accurately controlled.</p> |
