Second-order multifunction filter with fully differential current follower

This paper describes the design of a multifunction biquad filter that can provide multiple transfer functions according to the input and output current ports selected. The filter design is based on a general circuit with five passive elements (three of them are grounded) and one fully differential current follower. This versatile building block is ready to be manufactured by the ON Semiconductor Company and is expected to have impedance and transfer parameters close to the ideal ones in a wide frequency range. The functionality of the filter designed was verified by computer simulation and experimental measurement. The influence of real properties of the active element on the filter characteristics was ascertained.