Current-mode Universal Filter with Four Inputs and One Output using CDTAs

Abstract

A current-controlled multiple-input single-output current-mode universal filter employing current differencing transconductance amplifiers (CDTAs) as active elements is described. The proposed circuit offers the following attractive features: employment the minimum number of active and passive components; simultaneous realization of all the standard filtering functions; independent current-control of the parameters o,, and woIQ; no requirement of component matching conditions; employment of only two grounded passive capacitors which is suitable for integrated circuit (IC) implementation; and low passive and active sensitivities.

Current-mode universal filter and quadrature oscillator using CDTAs

“…Both of the filters consisted of 2 CDTAs and 2 capacitors and their structures were very simple; the filter in [10] was especially easy to cascade for high-order filters. However, the 2 filters could only realize low-pass (LP), band-pass (BP), and high-pass (HP) filter functions, and the HP in [10] and BP and HP in [11] were not at high-impedance output nodes, which need z-copy terminals to copy the currents to high-impedance terminals. The multifunction filter in [12] used too many active elements (more than 2 CDTAs).…”

“…The CDTA is a true current-mode element because its inputs and outputs are all in current form, possessing the advantages of current-mode circuits, and it is an excellent active block in resistorless analog circuit design. As a result, a variety of CDTA-based applications have been reported, such as universal filters [10][11][12][13][14][15], sinusoidal oscillators [16][17][18][19][20], multipliers and dividers [21], and current limiters [22].…”

“…A universal filter and a current-mode Kerwin-Huelsman-Newcomb filter were proposed in [10] and [11], respectively. Both of the filters consisted of 2 CDTAs and 2 capacitors and their structures were very simple; the filter in [10] was especially easy to cascade for high-order filters.…”

“…All of the works in [10][11][12][13][14][15][16][17][18][19][20] could only realize the universal filter or sinusoidal oscillator, and 2 important functions realized in the same circuit are rarely reported.…”