Modelling and optimization of active filters by hybrid VIV-MMC-graphs

Novel “VIV” signal flow graphs are introduced. They provide a description of active filter subblocks consisting of OpAmps with grounded inputs. The Tow-Thomas, the Åckerberg-Mossberg, the Fleischer-Tow, and MFB structures are typical representatives of such a filter class. Many kinds of active filter like the Sallen-Key utilize a more general OpAmp connection with ungrounded inputs. These circuits are well modelled by the modified Mason-Coates („MMC“) graphs. Finally, combined „VIV-MMC“ graphs are appropriate for the filters that compound both the grounded and ungrounded OpAmps. In virtue of these graphs three propositions are framed, which enable optimizing the component ratio and dynamic range. Key-Words: Active filter, optimization, signal flow graph, MC graph, MMC graph, „VIV“ graph, „VIV-MMC“ graph.