Analytical Synthesis of Low-Sensitivity High-Order Voltage-Mode DDCC and FDCCII-Grounded R and C All-Pass Filter Structures
The difficulty of realizing the operations of addition and subtraction of a voltage-mode signal renders two special active elements, namely, differential difference current conveyors (DDCCs) and fully differential current conveyors (FDCCIIs), both of which have the ability to perform the operations of addition and subtraction, to become very important for voltage-mode analog filter design. Note that, for the design of operational transconductance amplifier and capacitor (OTA-C) filters, the recently reported analytical synthesis methods (ASMs) have been shown to be very effective for achieving simultaneously the three criteria, namely, all capacitors being grounded, the use of the minimum number of active and passive components, and the use of single-ended input OTAs. However, none of the ASMs uses DDCCs and FDCCIIs in the design of voltage-mode filters. In this paper, a method of realizing DDCC and FDCCII-based all-pass filter structures with either equal capacitances or equal conductances through a new ASM is presented. Only n current conveyors (the least number of active components), n grounded capacitors, and grounded resistors (the minimum number of passive components) are used for realizing an nth-order voltage-mode all-pass filter structure. Moreover, the new all-pass filter structure synthesized by the new ASM achieves very low individual as well as near-null group sensitivities just as in the case of the passive LC ladder filters, has very low power consumption, a low component spread for equal denominator conductance design, and a high input impedance which is attractive from the point of view of cascadability. Finally, H-Spice simulations, using 0.35-mum process and plusmn1.65-V supply voltages, are included and validate theoretical predictions.