| 摘要 |
PURPOSE:To enhance the reliability of the title apparatus by providing a variable resistance circuit applying feedback to an amplifier capable of controlling a gain on the basis of an electric signal with definite resistance to make a resistance value variable and continuously changing the delay time of an active all-pass filter. CONSTITUTION:A delay circuit is constituted of an equivalent circuit consisting of passive elements such as an inductor L, a condenser C or the like and an amplifier. That is, the inductor L, the condensor C and an operational amplifier 12 are used to constitute an active all-pass filter of secondary order or more imparting a delay time at LC resonance frequency and a variable resistance circuit 6 applying feedback to an amplifier 13 capable of controlling a gain C on the basis of an electric signal with definite resistance R to make a resistance value variable is provided to the part of the resistor connected to the input terminal of the operational amplifier 12 and the resistance in the active all-pass filter is made variable by said variable resistance circuit 16. Therefore, a delay time can be continuously changed only by the electric signal applied to a control terminal 17 and the mixing of noise in other circuit parts is prevented and the reliability of this apparatus can be enhanced. |
