New VCT based active filter configurations and their synthesis

The quest continues for new circuits exhibiting improved features, particularly with the recent resurgence of interest in continuous time filters for high frequency applications. In this paper, attention is drawn to two new configurations based on the voltage-to-current transactor (VCT). This device, which operates as a transconductance amplifier with differential voltage input and floating current source output, was first proposed by C.S. Den Brinker et al. (1977), and early applications in filter design were demonstrated by J.K. Fidler et al. (1977). Whilst the device has not appeared commercially, simulation results have given sufficient encouragement for circuits based on discrete VCT realisations to be explored, and a second- and third-order all-pole low-pass filter are presented below