| 摘要 |
<p>PURPOSE:To constitute an A/D converter with no adjustment and less error by detecting the amplitude of a synchronizing signal from a video signal subject to digital conversion and applying negative feedback so that the amplitude is equal to a reference data. CONSTITUTION:A video signal clamped by a pedestal clamp circuit 4 is inputted to an A/D converter 5, converted into a digital signal 6 and fed to the next system and also fed to a synchronizing signal amplitude detection circuit 7. The synchronizing signal amplitude data 8 is integrated by an integration device 9, the level is compared with the reference data, the difference data is converted into an analog voltage by a D/A converter 10 to control the gain of a voltage controlled variable gain amplifier 3. When the synchronizing signal amplitude data 8 is larger than the reference data, the gain of the voltage controlled variable gain amplifier 3 is decreased, and when smaller, the gain is increased by constituting the negative feedback loop. Thus, no adjustment of the video signal amplitude is attained.</p> |
