One configuration for realizing voltage-mode multifunction filters and another configuration for realizing current-mode multifunction filters each using two current-feedback amplifiers (CFAs) are presented. The proposed voltage-mode circuit exhibits simultaneously lowpass, bandpass, and highpass filters. The proposed current-mode circuit also exhibits simultaneously lowpass, bandpass, and highpass filters. The proposed circuits offer the following features: no requirements for component matching conditions, low active and passive sensitivities, employing only grounded capacitors, and the ability to obtain multi-function filters from the same circuit configuration.

The applications and advantages in the realization of active filter transfer functions using current-feedback amplifiers (CFAs) have received considerable attention. This amplifier can provide constant bandwidth (independent of closed-loop gain) and a high slew-rate capability. Thus, it is beneficial to use a CFA as a basic building block to realize various analogue signal-processing circuits.

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In this paper, a new configuration is proposed to realize voltage-mode lowpass, bandpass, and highpass filters simultaneously by using two CFAs, two grounded capacitors, and five resistors. One (or two) more filtering signal can be obtained with respect to the previous two-CFAs biquads in [

A new configuration is proposed to realize current-mode lowpass, bandpass and highpass filters simultaneously. One more filtering signal can be obtained with respect to the previous current-mode biquad in [

Using standard notation, the port relations of a CFA can be characterized by

The proposed voltage-mode lowpass, bandpass and highpass filter.

Thus, the circuit realizes an inverting lowpass signal at

The gain constants are

One possible design equations for the specified

Under the design (

All capacitors are grounded in Figure

Taking into account the tracking errors of CFAs, namely

The active and passive sensitivities in Figure

The proposed current-mode circuit is shown in Figure

The proposed current-mode filter.

Thus, the circuit realizes an inverting lowpass signal at

Because the output currents are flowing in grounded elements, additional current followers are required for sensing and taking out the output currents. The active and passive sensitivities in Figure

The nonideal equivalent circuit model of the CFA is shown in Figure _{y} = 2 M

Nonideal equivalent circuit of the CFA includes the parasitic impedances.

where

From (

Note that the influence of the parasitic elements on the frequency responses of the current-mode filters in Figure

Experiments were carried out to demonstrate the feasibility of the proposed circuit. The CFAs were implemented using AD844s. Figures

Experimental frequency responses of Figure

In this paper, a configuration for realizing voltage-mode multi-function filters and another configuration for realizing current-mode multi-function filters using CFAs are presented. The proposed voltage-mode circuit exhibits simultaneously lowpass, bandpass and highpass filters by using two CFAs, two grounded capacitors, and five resistors. The proposed current-mode circuit exhibits simultaneously lowpass, bandpass, and highpass filters by using two CFAs, two grounded capacitors, and six resistors. The proposed circuits have no requirements for component matching conditions. The active and passive sensitivities are low.

The authors would like to thank the anonymous reviewers for their constructive criticisms to improve the manuscript.