SUMMARYIn this paper it is shown that active-RC filters whose sensitivity to component tolerances can be minimized by impedance tapering, will also have low output thermal noise. It is shown that impedance tapering will also reduce output thermal noise in OTA-C filters.

A generalized structure that is capable of implementing power-law filters derived from 1st and 2nd-order mother filter functions is presented in this work. This is achieved thanks to the employment of Operational Transconductance Amplifiers (OTAs) as active elements, because of the electronic tuning capability of their transconductance parameter. Appropriate design examples are provided and the performance of the introduced structure is evaluated through simulation results using the Cadence Integrated Circuits (IC) design suite and Metal Oxide Semiconductor (MOS) transistors models available from the Austria Mikro Systeme (AMS) 0.35 μm Complementary Metal Oxide Semiconductor (CMOS) process.

Summary The effect of coupling on the overall sensitivity to component tolerances of two second‐order resonators is compared with the sensitivity of a non‐coupled cascade of two second‐order resonators. Coupled resonators consist of two second‐order resonators “coupled” within a negative feedback loop. The resulting overall fourth‐order transfer function of the two circuits, coupled and non‐coupled, is identical. The “cascaded” poles, ie, the poles of the two cascaded resonators, are therefore identical to the poles of the coupled circuit, the coupled poles. The poles within the negative‐feedback loop, the “open‐loop” poles, will be different. We assume that the manufacturing technology used to realize the open‐loop poles of the coupled circuit is the same as that of the cascaded, non‐coupled circuit. The open‐loop poles will therefore be subject to the same component tolerances as those of the cascaded non‐coupled circuit. Our analysis leads to the optimum location in the s‐plane with regard to minimum sensitivity, for the open‐loop poles of the coupled circuit. Since resonators are essentially the equivalent of second‐order bandpass filters, the results obtained are applied to coupled second‐order active‐RC filters, or biquads, for which insensitivity to component tolerances is critical. The examples given pertain to the coupling of biquads.

The design procedure of low-sensitivity, low-pass (LP) Z"'-and 3'-ordcr class4 Sallm and Kcy active resistance-capacitance (RC) allpole filters, using impedance tapering, has alrcady bccn published [I]. In this paper desensitization using impedance tspcring is applied to HP and BP 2"*+rdcr filters. It is shown that HP filters haw dual properties to LP filters in the scnsc of sensitivity Among various topologies of BP filters, the bcst topology is proposed. The sensitivity of a filter bansfer function to component tolerances is examined using the Schoeffler sensitivity measurc as a basis for comparison. Monte Carlo runs are performcd as a double-check. The component values, selected for impedance tapcring, account for the considerable decrease in scnsitivitics to component tolerances for thc LP as well as for the HP and BP filters.

In this paper a comprehensive procedure for the analog modeling of Fractional-Order Elements (FOEs) is presented. Unlike most already proposed techniques, a standard approach from classical circuit theory is applied. It includes the realization of a system function by a mathematical approximation of the desired phase response, and the synthesis procedure for the realization of basic fractional-order (FO) one-port models as passive RC Cauer-and Foster-form canonical circuits. Based on the presented oneports, simple realizations of two-port differentiator and integrator models are derived. Beside the description of the design procedure, illustrative examples, circuit diagrams, simulation results and practical realizations are presented.