3. Summary

Theoretically, all active RC filter schemes can be realized as switched-capacitor circuits by replacing resistors with a set of switches and capacitors. In practice, however, most of the schematics thus obtained are not suitable for integration, as they are too sensitive to the influence of parasitic capacitances. This is particularly true of schemes using gyrators or FDNRs (Frequency Dependent Negative Resistance) (see ). At present, only implementations based on the use of an integrator as a basic circuit are used. Two main methods exist:

• operational simulation of an LC model filter using, in particular, the leap frog method (see ) ;

• the production of biquadratic cells and their combination, particularly in the form of coupled structures.

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