| 摘要 |
PURPOSE:To eliminate a potential difference between the DC potential and the clamp potential of an output at the time of muting and in a usual video signal period, by fixing a sample and holding circuit to a sample state and controlling an output voltage, at the time of muting. CONSTITUTION:In a state that no mute signal exists, an output of an outputting circuit 6 is compared with a reference voltage from a reference potential source 11 by a comparator 12, and provided to a sample and holding circuit 13. In the circuit 13, by a gate pulse applied to a terminal 15, a comparison voltage is sampled to a capacitor 18 in a gate pulse period, holding is executed in other period, and by controlling a variable DC shifting circuit 10 by this holding voltage, an outputted video signal is clamped. On the other hand, when a mute signal has been impressed to a mute signal input terminal 5, the potential from a DC potential source 8 passes through the circuit and appears in an output terminal 7. In this case, at the time of muting, the circuit 13 is fixed to a holding state, and the potential from the reference potential source 11 is outputted to the terminal 7. |
