| 摘要 |
PURPOSE:To smoothly perform the rise of a circuit at the time of applying a power source, by providing an AGC circuit in which follow-up to the fluctuation of an inputted high frequency signal level is accelerated immediately after applying the power source, and it is decelerated after a prescribed time. CONSTITUTION:The emitter resistance of a transistor Q1 is divided into resistors R1 and R2, and a capacitor C3 which decides the follow-up speed of the AGC circuit is connected in parallel with the resistor R2. And the capacitor C3 is separated immediately after applying the power source, and also, a transistor Q3, a resister R4, and a capacitor, C4 are provided to decelerate the follow-up speed by connecting the capacitor C3 in parallel with the resistor R2 after the prescribed time. Therefore, AGC is applied on an input signal without delay immediately after applying the power source, and thereby, it is possible to shorten a rise time until a video signal is demodulated normally. Also, even when noise is mixed just before a vertical synchronizing signal after the prescribed time, the flowing of an image on a monitor television can be prevented from occurring.
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