| 摘要 |
PURPOSE:To always obtain a correct reference time, by separating the synchronizing signals from the 1st clamping circuit to which video signals are supplied and detecting the reference time through the 2nd clamping circuit. CONSTITUTION:The signals supplied from a terminal 41 are applied to the middle point of connection between a resistor 43 and a constant current source 44 through a capacitor 42. The signals at the middle point are supplied to a differential amplifier 45. Thus a clamping circuit 40 is formed. At the same time, the signals sent from the terminal 41 are connected to a constant current source 72 through a capacitor 71 to form a clamping circuit 70. With these two circuits 40 and 70 of different time constants, a signal having the sink chip part set at a prescribed potential is obtained from the circuit 40 having a long time constant. Thus the vertical synchronizing separation is performed in an accurate way. While a signal with the noise suppressed at the pedestal part is obtained from the circuit 70 having a short time constant. Thus the front edge of a synchronizing signal is detected in an assured way. In such way, the reference time can be accurately detected. |
