Low-Sensitivity, Low-Power 4-Order Low-Pass Active-RC Allpole Filter Using Impedance Tapering

The analytical design procedure of lowsensitivity, low-power, low-pass (LP) 2-and 3-order class-4 active-RC allpole filters, using impedance tapering, has already been published [1][2]. In this paper the desensitisation using impedance tapering is applied to the design of LP 4-order filters. The numerical design procedure was performed by Newton’s iterative method. Analytically designed unity-gain LP 4-order filters [3] can provide initial values for Newton’s method. The sensitivities of a filter transfer function to passive component tolerances, as well as active gain variations are examined by the Schoeffler sensitivity and Monte Carlo PSpice simulation. Butterworth and Chebyshev 0.5dB filter examples illustrate the design method.