A multiple output active filter based on current followers

In this paper a multiple output current follower (CF)-based active filter ( MOCFF) is presented. The construction of basic filtering oriented biquadrat ic transfer functions (low-pass. high-pass, band-pass, band-notch and all-p ass) is realized by means of two independent stages of identical topology. Each of them incorporates three CFs appropriately interconnected with R,C b ranches; a CF-based adder (CFA) in conjunction with a versatile CF-incorpor ating mutual feedback symmetric circuit (MFSC) implement three different fr equency responses. The pair of CFs composing the MFSC should be visualized as a voltage transf er function generator. The MOCFFs salient feature is the current-based sign al processing while voltage remains the input and output variable. Taking i nto consideration the innate CF current tracking error, transfer function m odifications owing to CF non-ideality are provided. Our theoretical analysis is confirmed by HSPICE simulation results with the CF block function implemented by a properly modified pure CMOS CCII. The p roposed topologies, bring able to realize high quality factor frequency res ponses obtainable by three CFs, constitute a good choice for trading off be tween the desired multiple character. the number of necessary active elemen ts and a satisfactory performance.