Second-Order State-Variable Filter with Current Operational Amplifiers

A design of the second-order filter based on the state-variable canonic structure is described. The filter operates in current mode and offers low-pass and band-pass transfer functions simultaneously. Current operational amplifiers are used as main active building blocks. An analysis of the influence of amplifier real properties on the filter characteristics is presented. The shifts of filter poles and appearance of new parasitic zeros is observed. Computer simulation with a bipolar model of current operational amplifier was used for verification of the filter functionality.