Sensitivity considerations in a multiple-feedback universal active filter

Abstract

A multiple-feedback universal active filter is presented and evaluated on the basis of its sensitivity performance. This canonic realization provides, simultaneously, second-order low-pass, bandpass, and highpass outputs that may be combined to implement generalized biquadratic transfer functions. Additionally, it features the capability of local positive feedback to allow Q -enhancement with the ensuing advantages of sensitivity minimization and reduction in RC -element spread. A new analysis technique is developed for the evaluation of \omega_0 and Q sensitivities to operational-amplifier (OA) dc gain and gain-bandwidth product. This technique is extended to modify the figure of merit, introduced for sensitivity minimization purposes by Fleischer, and thus leads to easily obtainable expressions for optimum Q -enhancement factor and the corresponding value of Q in the absence of positive feedback. Making use of this sensitivity analysis technique, the new design is compared to two other high- Q filter configurations widely known for their excellent sensitivity characteristics. It is concluded that the new filter exhibits comparable performance especially in higher tolerance applications using wide-bandwidth OA's.