A procedure for the design of allpole filters with low sensitivitynto component tolerance is presented. The filters are based onnresistance-capacitance (RC) ladder structures combined with singlenoperational amplifiers. It is shown that by the use of impedancentapering, in which L-sections of the RC ladder are successivelynimpedance-scaled upwards, from the driving source to the amplifierninput, the sensitivity of the filter characteristics to componentntolerances can be significantly decreased. Impedance tapering isnachieved by the appropriate choice of component values. The designnprocedure, therefore, adds nothing to the cost of conventional circuits;ncomponent count and topology remain unchanged, whereas the componentnvalues selected for impedance tapering account for the considerablendecrease in tolerance sensitivity
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