Current-Mode High Output Impedance Multifunction Filters Employing Minimum Number of FTFNs

In this study, five current-mode FTFN-based multifunction filters are proposed, which realize the same transfer functions in ideal case. All circuits employ two capacitors and three resistors. For each circuit R-C:C-R transformation increases the number of realization possibilities to ten. The proposed topologies simultaneously realize three basic filtering functions using minimum number of FTFNs and provide high output impedances that enable easy cascading in current mode. Sensitivity analysis of the filters show that they have low passive sensitivities, ω0, Q and ω0/Q of the filters are insensitive to current tracking errors, furthermore ω0 of the filters are insensitive to voltage tracking errors of the FTFNs. The proposed circuits do not require component matching condition except for notch and allpass responses and permit independent adjustment of ω0 without disturbing ω0/Q. Experimental and simulation results are given to verify the theoretical analyses.