| 摘要 |
PURPOSE:To attain optimum tracking against the change in lightness of an objective by providing a limiter to an AGC circuit for a luminance signal and applying feedback to the filter. CONSTITUTION:The luminance signal is fed to a detecting circuit 11 and its detected output is fed to a base of a transistor (TR)Q11. Switches S2-S5 are connected to the contact A position at the AGC operation. The larger the level of the luminance signal from an amplifier 3 is, the larger output current Ia is extracted from a differential amplifier 41 and an AGC voltage in response to the current Ia is obtained. In selecting the switches S2-S5 to the L position, the AGC voltage at that point of time is held in a memory 20. Feedback is applied to the input of the limiter circuit 14. The change in the AGC voltage is kept within the tracking range of an AGC circuit 10 to avoid insensible region at manual operation or rapid change in the gain of the amplifier 3.
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