| 摘要 |
PURPOSE:To stabilize a sampling clock and to make it secure by using an oscillation output having a constant frequency instantaneously locked in phase with synchronization information included in the input video signal as the sam pling clock of an input video signal. CONSTITUTION:A horizontal synchronizing signal (b) is separated from the input video signal from a terminal 10 to be outputted, and the pulse (c) of the prescribed time width is outputted at a monostable multivibrator circuit 12. The video signal is separated from a burst signal, and supplied to an NAND gate 13. Therefore, only a burst pulse (d) based on the burst signal is outputted from the NAND gate 13 and supplied as a command signal for starting the oscillation of an oscillating circuit 50 to a terminal S. Since a control voltage VC is supplied to other terminal V, a control voltage VC controls variably the oscillation frequency of the oscillating circuit 50, and an oscillation start phase is instantaneously decided and multiplied and outputted as the sampling clock.
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