Low-sensitivity, low-power 4/sup th/-order low-pass active-RC allpole filter using impedance tapering

The analytic design procedure of low-sensitivity, low-power, low-pass (LP) 2/sup nd/- and 3/sup rd/-order class-4 active RC allpole filters, using impedance tapering, has already been published (Moschytz, 1999). In this paper the desensitisation using impedance tapering is applied to the design of LP 4/sup th/-order filters. The numerical design procedure was performed by Newton´s iterative method. Analytically designed unity-gain LP 4/sup th/-order filters (Jurisic et al., 2004) can provide initial values for Newton´s method. The sensitivities of a filter transfer function to passive components tolerances, as well as active gain variation are examined by the Schoeffler sensitivity and Monte Carlo PSpice simulation. Butterworth and Chebyshev 0.5dB filter examples illustrate the design method.