| 摘要 |
PURPOSE:To guarantee the output potential of the titled circuit and to stabilize the operation of the circuit by detecting a signal other than a video signal upon its incoming, and clamping the DC level of the detected signal at a prescribed potential forcibly. CONSTITUTION:In case the presence of a gate pulse is identified by a signal interruption detection circuit 8, a switch SW1 is connected to a terminal (a), and a feedback loop is formed by a feedback circuit 5 to which a reference voltage Vref1 is set, and the point of a horizontal synchronizing signal is clamped in a prescribed constant level corresponding to the reference voltage Vref1. On the other hand, when the absence of a gate pulse is identified by the circuit 8, the switch SW1 is connected to a terminal (b), and a feedback loop is formed by a feedback circuit 7 to which a reference voltage Vref is set, and the output DC level of a video amplifier 4 is clamped in a prescribed constant level corresponding to the reference voltage Vref. In case there is no video signal, or in case a signal lacking a horizontal synchronizing signal comes in, the output DC potential of the circuit is secured in a prescribed level.
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