Current-Mode First-Order Highpass, Lowpass, and Allpass Filters Using Two ICCIIs

CFOA‐based simple mixed‐mode first‐order universal filter configurations

“…From Table 1, the following may be noted: The circuits of previous works 2,29–43 use more than one ABB, two ABBs 2,29–42 and three ABBs, 43 and, hence, do not belong to the class of single‐ABB‐based first‐order UAFs to which the circuits proposed in this article belong to. The single‐ABB‐based earlier works 3,10,12–14 use only a single ABB but realize a UAF only in CM, whereas other studies, 16–27 too, use only one ABB but realize an UAF only in VM. On the other hand, the single ABB configuration of Chaturvedi and Kumar 11 is in CM/TAM mode, whereas single ABB configuration of Maheshwari et al 15 and Singh et al 24 are in VM/TAM mode. None of the building blocks employed in previous works 3–24,26,27 are yet available as off‐the‐shelf ICs. The circuits of previous studies 5,14,20–22,24–27 do not employ a grounded capacitor. The UAFs in previous works, 5,16–19,21,23–25,27 do not have the appropriate Z in or Z out to enable cascadability. The only other earlier work which is based upon the use of a commercially available IC (namely, the LT1228 comprising an OTA followed by a CFOA) also realizes only VM UAF and does not employ a grounded capacitor. …”

“…A brief overview of earlier published first‐order UAFs is now in order. However, in order to keep the overview of the earlier works 2–43 as brief as possible, we have compiled the relevant data in tabular form as shown in Table 1.…”

“…i. The circuits of previous works 2, [29][30][31][32][33][34][35][36][37][38][39][40][41][42][43] use more than one ABB, two ABBs 2,29-42 and three ABBs, 43 and, hence, do not belong to the class of single-ABB-based first-order UAFs to which the circuits proposed in this article belong to. ii.…”

Single‐differential difference current conveyor‐based first‐order VM/TAM universal filter and its applications

“…First‐order filters have a wide range of applications in various fields such as (i) control systems, where they are used to remove unwanted variations in the output of a system, such as in temperature and pressure control and also in the design of lead/lag compensators (ii) communication systems, where they are used to remove unwanted frequencies from a signal, such as in radio or telephone systems, (iii) power electronics systems, to smooth out pulsating DC power, such as in a rectifier, (iv) electronic systems, where they are used in the design of higher order filters, oscillators, and other circuits 1 . In the open literature, a number of first‐order universal filter configurations have been reported using several commercially available ICs such as op‐amp, current feedback amplifier, operational transconductance amplifier, LT1228, and other modern active building blocks (ABB) 2–50 A comparison table including various features of the previously reported first‐order universal filters employing various ABBs is tabulated in Table 1.…”

“…2,29–47 use more than one active device. Grounded capacitors are not employed in the design of the circuits of Refs. 4,5,8,14,20–22,24,33,34,43,47,49 More than three resistors are used in the circuits of Refs. 2,37,38,43,46 Independent controllability of gain and cutoff frequency is not available in the circuits presented in Refs.…”