Realization of current-mode biquadratic filter using CC IIs with current followers

This paper proposes the circuit configuration of a current-mode biquadratic filter which uses a pair of four-terminal active-current conveyors (CFCC II) consisting of a current follower attached to a second-generation current conveyor (CC II). the circuit is composed of one current adder and two current integrators. This configuration is capable of synthesizing arbitrary current-mode second-order transfer functions by changing the conditions (grounding or connecting) at the output terminals of the CFCC IIs. Each of the proposed filters has high output impedance so they can be cascaded directly. Moreover, ω0 and Q0 is determined from the ratio of passive elements, and the element sensitivity is even lower than 0.5. Since all the passive elements are grounded, this configuration is very advantageous to IC fabrication. Again, the effect of imperfection of CFCC II on the transfer function is studied and it is found that ω0 is influenced by the current conversion factor of CFCC II and Q0 is affected by the imperfection of the integrator. Moreover, it is shown that the operating frequency limits of the filter are determined by the permissible change of Q0. Each type of filter actually is synthesized, and the useful operation is confirmed by experiments.