| 摘要 |
PURPOSE:To extend the ACC interlocking range for a weak input by obtaining the output in the high level when the level of a burst signal is low and lowering the output level quickly and lowering it gently thereafter when the level of the burst signal is lower than a certain value. CONSTITUTION:A signal obtained by synchronous detection of the burst signal is inputted to an input terminal 8, and the DC level of this signal is lowered when the input is increased. The difference between a color killer level and the ACC level of an automatic color saturation adjusting circuit is defined as V0. When a minimum level (burst level) of this signal is lower than the voltage of the first reference power source 16, a transistor TR 9 is turned off and a TR 10 is turned on in the first differential amplifier 100. If the voltage of the second reference power source 26 is set to the ACC filter voltage which is obtained when the burst level about +6dB higher than an ACC MIN level is inputted, the characteristic shown by dotted lines in the figure is obtained. That is, the ACC interlocking range is extended though the effect of the ACC circuit is weakened apparently in a weak electric field.
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