| 摘要 |
<p>PURPOSE:To accurately adjust the clamp potential of a pedestal level of a video signal and to eliminate a need for manual adjusting by sampling the digital value which is a converted pedestal level, and by comparing it with a reference value to adjust the clamp potential of a clamp circuit. CONSTITUTION:The input terminal of a register 11(R) is connected to the succeeding stage of an A-D converting circuit 4, so that the digital value of the pedestal level (d) of the video signal converted by the circuit 4 is sampled by a clamp pulse supplied to a clamp pulse input terminal 9 to be stored in the register 11(R). The sampling value in the register 11 and the reference value supplied to a reference signal terminal 12 are compared by a digital comparator 13 that functions as a comparing circuit. And the output signal of the said comparison from the comparator 13 is supplied to an analog switch 14. To this switch 14, a voltage source of positive voltage 15 and that of negative voltage 16 are connected, so that positive or negative voltage is supplied to an integrating circuit 17 as suitably weighting in response to the comparison- output signal from the digital comparator 13.</p> |
