| 摘要 |
PURPOSE: To provide a circuit device which has an electronically controllable transfer characteristic. CONSTITUTION: An operational amplifier 1 which has controllable negative feedback has a non-inverted input terminal 2 and an output terminal 3, connected to a voltage divider circuit having a frequency dependence, and plural taps 9 to 12 and 31 to 35 are provided which connect to an inverted input terminal 16 of the operational amplifier through a first electronically controllable switch 8 and are connected to an output 36 of this device through a second electronically controllable switch 30. The first switch 8 and the second switch 30 are controlled so that an input signal in a frequency band which has in influence upon different filter curves and is determined by the frequency- dependent voltage divider is boosted. The second switch 30 is set to such position that attenuation can be obtained for a desired frequency band width, and the first switch 8 is set to position such that a desired degree of attenuation can be obtained. |
