| 摘要 |
PURPOSE:To prevent the saturation of a magnetic tape and to reduce the overshoot, by quickening the response to a large amplitude input at high frequencies, in a detector used for the noise reduction system of the compander system. CONSTITUTION:A signal applied to an input terminal IN is converted into a current level at a full-wave rectifying circuit 11, rectified and applied to an average circuit 13, and current/voltage conversion circuits 14 and 15 respectively. When a high frequency large amplitude input is applied to the input terminal IN rapidly, a switching element S2 is turned on instantly to make the input terminal level of an average circuit 13 almost equal to an output terminal level of an HPF17. As a result, the gain of a variable gain amplifier is controlled more quickly and lower, the overshoot of an encoder at high frequencies is reduced. The generation of the overshoot due to a signal of a large amplitude is suppressed by turning on a switching element S1. |
