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A current-mode low input and high output impedances first-order allpass filter using two multiple output second-generation current conveyors (MOCCIIs), one grounded capacitor and one grounded resistor is presented. The suggested filter uses a canonical number of passive components without requiring any component matching condition. The frequency responses simulation results of the proposed filter confirm the theoretical analysis.

Current conveyors (CCs) are receiving much attention for their potential advantages such as inherent wider signal bandwidths, simpler circuitry and larger dynamic range [1,2]. Current-mode active filters with low input impedance and high output impedance are of great interest because they can be directly connected in cascade to implement higher order filters [3,4]. Besides the use of only grounded capacitor and resistor are beneficial from the point of view of integrated circuit fabrications [5,6]. Several current-mode first-order allpass filters using various active components have been reported. Some circuits use two current conveyors to realize such a firstorder allpass filter function with high output impedance [7-9]. However, the passive components they used are not canonical and they require passive components matching conditions [7,8]. Moreover, these circuits [7-9] have not the advantage of low input impedance. The first-order allpass filters [10,11] each uses two current conveyors, one grounded capacitor and one grounded resistor with low input and high output impedances. The first-order allpass filter [

In this paper, a new current-mode first-order allpass filter using two multiple output second-generation current conveyors (MOCCIIs), one grounded capacitor and one grounded resistor are presented. The proposed circuit has the advantages of low input and high output impedances and without requiring any element matching condition.

The rest of the paper is presented as follows. In Section 2 we present the proposed current-mode first-order allpass filter circuit. Section 3 discusses the active and passive sensitivities of the proposed filter. Section 4 discusses the influences of parasitic elements on the proposed circuit. The frequency responses simulation results are presented in Section 5. Section 6 concludes the paper.

Using standard notation, the port relations of a MOCCII can be characterized by v_{x} = v_{y}, i_{zk} = ±i_{x} and i_{y} = 0. Considering the proposed current-mode circuit in

From (1) it can be seen that a first-order allpass response is obtained from I_{out}. Because the input terminal of the proposed first-order allpass filter is connected directly to the x terminal of MOCCII (1) and the y terminal of MOCCII (1) is grounded, the input terminal has the advantage of low input impedance. Because the I_{out} output terminal is taken out directly from the z_{22+} terminal of the MOCCII (2), the I_{out} output terminal has the advantage of high output impedance. The proposed circuit uses only one grounded resistor and one grounded capacitor, the use of only grounded capacitor and resistor are beneficial from the point of view of integrated circuit fabrications [5,6].

Taking into consideration the MOCCII non-idealities, the port relations of MOCCII can be expressed as

where and denotes the current tracking error, and is the input voltage tracking error of a MOCCII. Reanalysis of the filter circuit in

The cutoff frequency is obtained by

The active and passive sensitivities are low and obtained as;.

A non-ideal MOCCII model is shown in

where, ,

.

In Equation (5), undesirable factors are yielded by the non-idealities of the MOCCIIs. The effects of capacitance C_{z}_{12} become non-negligible at very high frequencies. To minimize the effects of the MOCCIIs’ non-idealities, the operation angular frequency should restricted to the following condition

HSPICE simulations were carried out to demonstrate the feasibility of the proposed circuit in

_{c} = 3.979 MHz: C = 10 pF and R = 4 kΩ. The power supply was ±1.25 V. The bias voltages are V_{b} = –0.6 V.

A new current-mode first-order filter configuration using two MOCCIIs, one grounded capacitor and one grounded resistor is presented. The proposed circuit has the advantages of low input and high output impedances, using grounded passive components and without requiring any element matching condition.