| 摘要 |
PURPOSE:To obtain a reproducing picture image with high picture quality by changing the charging time constant depending on the difference between a black level and a reference level of a picture signal whose DC component is lost, decreasing the charging time constant at the sudden change period of the black level to suppress transient phenomenon and increasing the charging time constant to prevent lateral noise. CONSTITUTION:A picture signal whose DC component is lost is DC-regenerated from an inpu terminal 6 via a low impedance circuit 5, a capacitor 8 and a high impedance circuit 9, the DC-regenerated picture signal is obtained at an output terminal 10, a clock pulse is supplied from an input terminal 13 and a switching circuit 12 is conductive by the clock pulse. A voltage having a reference level Vo to be clamped is impressed to a power terminal 14, and when the circuit 12 is conductive, a charging current flows to the capacitor 8 via the switching circuit 12 and a nonlinear resistor 11 and capacitor 8 is charged so that the reference level Vo is set. |
