| 摘要 |
PURPOSE:To obtain a tracking device whose loop gain is scarcely varied even with a variation of an input signal, by providing an AGC circuit consisting of a multiplier and an error amplifier, on an output terminal of a detector. CONSTITUTION:When an input signal S/N drops, an output of a detector 9c also drops in proportion to it. Accordingly, an output of a multiplier 9m also works on the dropping direction, but when it is set in advance in the direction where an output of an error amplifier 9n increases when it becomes lower than a set voltage of the error amplifier 9n, a gain of the multiplier 9m increases, the output of the multiplier 9m acts so as to increase, and after all, the output of the multiplier 9m is balanced at a value of the set voltage of the error amplifier 9n. This action is the same even in case when the signal S/N has increased. In this way, by keeping the input level of a synchronizing detector 9d constant, the loop gain becomes constant. |
