An improved technique for realization of switched-capacitor filters from LC networks

Abstract

A systematic approach for the synthesis of switched-capacitor (SC) filters is presented based on (1) the nodal potential relation of passive doubly terminated LC networks (i.e., LC filters), represented in matrix form using a virtual vector to express the variables; (2) switched-capacitor fundamental blocks constructed with customary SC integrator circuit structures. The main feature of our new technique is its capability to realize SC filters without delay-free loops. This characteristic improves the transfer function estimation of the active components used. This method is well suited to the mass production of integrated SC filters using the programmable capacitor matrix (PCM), which can result in substantial savings in production time and costs. It is also shown that this method can be extended to directly transforming passive all-passes to SC all-passes.