Unified Methodology for Realizing Fully-Differential Current-Mode Filters

Using the concept of nullors, an unified methodology is presented which can be used for realizing fully differential current mode filters using a variety of building blocks which can be represented by nullators and norators. The workability of the proposed approach is verified by the SPICE simulation results of an exemplary universal biquad made from multiple-output-currentconveyors. This exemplary filter can realize low pass (LP), high pass (HP), band pass (BP), band elimination (BE) and all pass filters-all in fully differential form, from the same topology. The angular frequency and ω0/Q0 or Q0 of the realized filters are orthogonally controllable. The applicability of the developed approach to derive a variety of biquads as well as higher order FD CM filters (including the electronically-tunable ones), using a number of other building blocks such as FTFNs, Current Conveyors, Controlled Current Conveyors and OTAs, is conceptualized. Key-Words: nullors, fully differential filters, current-mode circuits, current conveyors, operational transconductance amplifiers.