| 摘要 |
A polar leapfrog filter includes at least one polar network. The polar network comprises a differentiator constituted by an operational amplifier having input and output terminals, and a first integrator formed by a first capacitor for providing negative feedback to the operational amplifier and a first variable transconductance amplifier; and a second integrator formed by a second capacitor for providing negative feedback to the first integrator, and a second variable transconductance amplifier. A differentiator is provided at each of the input and output portions of the filter, and a third differentiator is provided immediately preceding the output side differentiator. In the case where two or more said polar networks are incorporated, an additional differentiator is provided between the polar networks. The sum of the number of the circuits constituting the differentiators and the number of the polar networks is selected to be even and equal to the order of the filter. The adjacent ones of the circuits are connected in such a manner that leapfrog type negative feedback is effected, and the differentiators except the output side one are constructed in the form of self negative feedback type.
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