Digitally programmable mixed mode universal filter using followers-a minimal realization

Abstract

A novel digitally programmable mixed mode universal filter capable of operating in all the four modes namely voltage, current, transimpedance and transadmittance mode is presented in this paper. The proposed filter is reconfigurable to realize all the five second order filter functions without any change in hardware. The filter is fully programmable as all its parameters namely pole frequency, quality factor and gain are independently controlled. Other attractive features of proposed configuration include cascadability (except for voltage mode), no component matching constraint and lesser parasitic effects. For providing all these features, it uses seven current/voltage followers, three switches, two to four resistor (depending on the mode) and two grounded capacitors only. The component count is proved to be minimal in the class of programmable filters offering comparable set of features.