| 摘要 |
In an active second-degree RC band-stop filter, six complex conductance elements are connected in series for tuning its stopping frequency, the first conductance element being an effective conductance, the second one being a capacitance, the third being the parallel connection of an effective conductance and a capacitance, the fourth being a capacitance, the fifth being an effective conductance and the sixth consisting of the parallel connection of an effective conductance connected to earth and an effective conductance connected to the free end of the first effective conductance, and the first effective conductance and the effective conductance of the third conductance element being tunable in synchronism with one another, and the input quantity being applied at the free end of the first effective conductance with respect to earth and the output quantity being taken from the junction between the second and the third conductance element with respect to earth; at the junction between the second and third conductance element, the output of a first amplifier with two inverted inputs is connected and at the junction between the fourth and fifth conductance element the output of a second amplifier with two inverted inputs is connected, these inverted inputs of the two amplifiers being connected to the remaining junctions of the conductance element series circuit in such a manner that the voltages at these remaining junctions are equal.
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