Towards a Perfect CMOS CCII

DC offset and inaccurate voltage follower action betweenterminals Y and X, the relatively highimpedance seen at terminal X and inaccurate currentfollower action between terminals X and Zplague simple circuit realizations of the CCII. This paper summarizesthe methods employed and compares the improvement of the CCIIcharacteristics achieved by a variety of published circuits,with emphasis laid on CMOS realizations. In these comparisons,the conventionally employed but inaccurate current mirror outputstages were replaced by a circuit employing current isolationand thereby providing accurate current follower action betweenterminals X and Z. Furthermore, twonovel realizations of a differential CCII – basedtransconductance amplifier are described, which can also be employedas input stage of an instrumentation voltage amplifier exhibitingan exceptionally high CMRR and excellent frequency response.Finally, a current fan out circuit for cascode CCII –‘swill be introduced, whose transfer function value is electronicallyadjustable.