2. ReviewCurrent conveyor-based first-order all-pass filters had been researched to a certain extent at the time when authors’ first selleckchem work was communicated in late 1998. It is apparent from the survey carried out in that work, which appeared in literature in 2000 [1]. The work of [1] provided a new impetus to the research in the area. A second generation current conveyor of negative type (CCII?) was used to realize first-order all-pass function, with a floating capacitor and two grounded resistors. It was, for the first time, that the idea of employing translinear conveyor for all-pass function was also given therein [1]. The single translinear conveyor-based circuit with two passive components was minimal at the time and continues to compete with most recent work, as shall follow later.

Soon, third generation current conveyor was next used for realizing not only voltage mode function but also current-mode filters [2]. One of the two voltage-mode circuits in [2] had its gain adjustment (��1) featured by employing four passive elements in all, whereas the other circuit used same component count as the first [1] work. Current-mode circuit with only two passive elements was a first attempt employing third generation current conveyor (CCIII) [2]. Although for sensing the output current, an additional active element was required. The CCIII-based circuits enriched the application of this active element, which had been only rarely used till then, as is also evident from the references cited therein [2].

A dedicated current-mode paper was then reported using CCIII and two passive elements for four new all-pass sections, with similar output current sensing requirement as before [3]. Almost at the same time, translinear-C current mode all-pass sections also appeared, which used translinear conveyor (current controlled conveyors, CCCII) and capacitor [4]. The circuits in [4] were electronically tunable through bias current of CCCII in a wide frequency range. However, independent access to the output current again required additional current follower. Another work followed where three different circuits were proposed with the feature of operability in either voltage or current mode, without changing the circuit configuration [5]. Starting with a CCII? based network, a translinear conveyor-based circuit and then a translinear-C version were given, along with an application in realizing quadrature oscillator.

The translinear-C circuit was electronically tunable. The paper demonstrated the use of a CCCII? for realizing a floating tunable resistor for the first time.All works mentioned above were based on the use of floating capacitor [1�C5]. In 2006, grounded capacitor-based first-order all-pass filter using a relatively Entinostat more complex active element, fully differential current conveyor (FDCCII) were reported [6]. Six distinct circuits providing first-order functions, with both voltage and current outputs, were proposed.