A technique for obtaining differential active filters suitable for integrated circuit implementation is presented. These filters, based on current-mode differential-wave active blocks, can operate at high frequencies. The cutoff frequency can by tuned by the bias current. The proposed filter topologies are modular and very flexible for both the electronic and the physical design. Simulation results of a third-order elliptic filter, designed in a 0.35-/spl mu/m CMOS technology, are presented.