Later, FDCCII was employed for realizing this function with better twice characteristics, as shall follow in chronological order.The year 2007 saw many works in the form of both current and voltage modes. Translinear-C all-pass sections in current-mode with accessible outputs at high impedance nodes enjoyed electronic tunability and high frequency operation [7]. Quadrature oscillator applications confirmed the utility of proposed all-pass sections, but the drawback of employing floating capacitor again turned out to be a blessing in disguise like other work [1�C5]. It ensured easy high frequency signal transmission from input to output node through ideally shorted capacitor (at high frequencies), bypassing the active element and hence its frequency limitations.

Another current-mode work became available with the advantage of employing two grounded components, easy for integration, and an active element in the form of a modified DVCC with a topology compatibility with CCIII as well [8]. This paper [8] introduced the concept of modified DVCC with a current transfer gain fromXtoZterminal of ��2�� instead of traditional ��unity�� value. However, input current insertion at two nodes necessitated additional current follower block for practical purpose [8]. Next, CDBA-based voltage-mode all-pass filters were reported in the same year with the advantage of low output impedance [9]. CCCDBA had already been proposed by the author; hence, the new circuits [9] were shown to be compatible with the new active element and hence electronically tunable.

CCCDBA-based circuits employed only two passive components and provided new directions for further study on tunable realizations using the active element.None of the voltage-mode circuits discussed so far [1�C3, 5, 6, 9] exhibited high input impedance and use of only grounded passive components. The work based on two DVCCs with onlyZ+ stages and three passive grounded components contributed six circuits each enjoying high input impedance as well [10]. High input impedance allowed easy cascading within a voltage mode system, while grounded components ensured fabrication ease. The former feature was demonstrated in quadrature oscillator design therein [10]. Very soon similar work appeared where six distinct circuits with high input impedance were proposed [11]. The matching requirements in [10] were in a ratio of ��2��, whereas the same in [11] required a ratio of ��1.

�� The circuits of [11] were more practical by the way of employing a resistive or capacitive termination Brefeldin_A at the outputZnode, unlike the circuits of [10], where the output appeared at high impedance node (Z) with no terminations. The catalogue of 12 circuits [10, 11] provide a new advancement to the knowledge on DVCC-based realizations, which was further enriched by a current-mode paper with one DVCC and two grounded components [12].