| 摘要 |
PURPOSE:To obtain a black level of a suitable video signal even from a TV signal under a weak electric field strength, by controlling the switching of two switches with a clamp pulse applied to a clamping transistor (TR). CONSTITUTION:When a video signal mixed with noise is inputted to a terminal 1, this signal is applied to the base of a buffer TR2, noise component is eliminated at an LPF11 and the result is applied to the base of a buffer TR8. When a clamp pulse is inputted from a terminal in a prescribed timing, a switch 9a is turned off and a switch 9b is turned on. Thus, a signal eliminated with noise is given to a capacitor C1, a clamp TR4 is conductive only during this period and the capacitor C1 is charged. Further, the switch 9a turns on and the 9b turns off in other than the clamp period, and signals passing through the TRs 2 and 8 are synthesized after passing through a switch 9, and noise can be eliminated. |
