| 摘要 |
PURPOSE:To reproduce stably a DC by providing a bias path for a current flowing into a DC stopping capacitor from a load side in order to minimize charges built up in the DC stopping capacitor during non-clamp period. CONSTITUTION:A video signal inputted from a terminal A is amplified by an emitter grounding amplifier 1, and only its AC component is transmitted to a clamp circuit through the DC stopping capacitor 4. When a clamp pulse is not inputted to a terminal B, charges are built up in the DC stopping capacitor 4 through a bypass transistor 11. The discharge is executed by a base current, and therefore its amount comes to an extremely small amount. Then, when the clamp pulse is inputted to the terminal B, a clamp transistor 12 is conducted to interrupt the bypass transistor 11, whereby charges built up during non-clamp period are pulled out of the DC stopping capacitor 4, and a potential at the cathode side of the capacitor 4 equals that of a clamp power source 5.
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