| 摘要 |
PURPOSE:To prevent a lock phenmenon, by maintaining the AGC voltage obtained immediately before the arrival of noise when an excessive noise is supplied. CONSTITUTION:Both the reference potential VREF1 and a video signal Vi are applied to a differential amplifier 5 to produce the AGC voltage VAGC at the output. When the voltage Vi containing a large noise arrives, a switching diode 20 conducts to turn off a transistor (TR)26 of a differential amplifier 17 and to turn on a TR27 respectively. As a result, a TR21 is turned on with an output TR29 turned off. Accordingly the AGC voltage produced by the amplifier 5 is not delivered. In this case, the voltage VAGC is maintained at the level obtained immediately before the arrival of noise. |
