Electronically tunable current - mode second - order universal filter using minimum elements

Abstract

This comment, relates to a recently published paper by M. Sagbas and K. Fidanboylu (see ibid., vol.40, p.2-4, 2004) which presents a current-mode second-order universal filter for realising lowpass, bandpass and highpass responses. This filter employs two second-generation current controlled conveyors (CCCIIs) and two capacitors. It is shown here that this circuit is not new, simply derived from another filter proposed by S. Ozoguz and C. Acar (see ibid., vol.33, p.948-9, 1997), employing CCCIIs instead of second-generation current conveyors (CCIIs).