NEW TECHNIQUES FOR THE DESIGN OF BILINEAR SWITCHED-CAPACITOR LADDER FILTERS.

摘要

Switched-capacitor filters have become very popular in recent years. this popularity was prompted by the facts that they are fully integratable using MOS technology and they possess important characteristics such as small size, clock controlled frequency response, ease of manufacturing, etc., which are essential in practical applications.;Existence of delay-free loops in SC ladder filters is one of the major factors limiting the performance of these structures. Three general techniques to break up delay-free loops in bilinear SC lowpass filters are presented. These techniques are extended and generalized for bilinear SC highpass and lowpass ladder structures. A general comparison among all three techniques for each case is carried out and the advantages and drawbacks are discussed.;A variety of new input stages which are parasitic insensitive are presented. These stages are compatible with both the direct and structures without delay-free loops (SWDFL) realizations. Two of them also perform S/H function.;Two general techniques to replace toggle-SC's with parasitic-insensitive SC's in SWDFL realizations are suggested.;The purpose of this research is to introduce new techniques and to improve and modify the existing techniques for the design of bilinear SC ladder structures which are derived from doubly-terminated analog models.;A new design technique to obtain an even-order bilinear SC lowpass filter with the minimum possible required opamps is presented.;A novel technique is introduced for the design of odd-order completely-parasitic insensitive SC highpass ladder filters. A new input stage is presented which also performs the S/H function in these structures. The design technique is extended to the even-order case.;For moderate to very wideband bandpass filters, a new design technique is presented which is based on a pseudo-N-path concept. The number of required opamps is reduced to half at the cost of increasing the number of the clock phases.;The computer program SCAR is utilized to verify the design techniques and also to find the sensitivities of the filters to element values and the finite gains of opamps.