A novel currentmode firstorder allpass filter with low input and high output impedance feature is presented. The circuit realization employs a single dualXsecondgeneration current conveyor, one grounded capacitor, and one grounded resistor, which is a minimum component realization. The theoretical results are verified using PSPICE simulation program with TSMC 0.35
Currentmode circuit design using current conveyor has received a considerable attention owning to its potential advantages such as wider dynamic range, greater linearity, wide bandwidth, simple circuitry, and low power consumption [
Comparison of various currentmode allpass filters.
References  No. of active elements  Single active element  No. of resistors and capacitors  Allgrounded passive elements  Low input impedance  High output impedance  Component matching constraint 

Higashimura and Fukui [ 
1CCII  Yes  4  No  No  Yes  Yes 
Higashimura [ 
1FTFN  Yes  3  No  No  No  Yes 
Toker et al. [ 
1CDBA  Yes  2  No  No  Yes  No 
Maheshwari and Khan [ 
1CCIII  Yes  2  No  No  No  No 
Kilinç and Çam [ 
1COA  Yes  2  No  No  Yes  No 
Minaei and Ibrahim [ 
1DVCC  Yes  3  No  No  Yes  Yes 
Khan et al. [ 
2MOCCII  No  2  Yes  No  Yes  No 
Maheshwari [ 
1DVCC  Yes  2  Yes  No  Yes  No 
Minaei and Yuce [ 
2DOCCII  No  2  Yes  Yes  Yes  No 
Minaei and Yuce [ 
1DXCCII  Yes  4  Yes  No  Yes  Yes 
Beg et al. [ 
1DXMOCCII  Yes  4  Yes  No  Yes  Yes 
Proposed Circuit  1DXMOCCII  Yes  2  Yes  Yes  Yes  No 
In this paper, a novel cascadable currentmode (CM) firstorder allpass filter is proposed. The circuit uses a dualX second generation multioutput current conveyor (DXMOCCII), a grounded resistor, and a grounded capacitor, which is ideal for IC implementation. The circuit offers lowinput impedance and highoutput impedance feature and also free from matching constraints. Nonideal gain and parasitic effects of the DXMOCCII on the transfer function of the proposed filter are also analysed.
DualX secondgeneration current conveyor [
Symbol of DXMOCCII.
The proposed currentmode (CM) firstorder allpass filter employing a DXMOCCII, a grounded capacitor, and a grounded resistor is shown in Figure
Proposed cascadable currentmode firstorder allpass filter.
The frequencydependent phase response of (
The salient features of the proposed circuit are the use of single active element, two grounded passive components, and providing low input and high output impedance. As all the passive components used are in grounded form, it is suitable for integrated circuit implementation and also reduces the associated parasitic effects [
By interchanging the resistor (
Taking the nonidealities of the DXMOCCII into account, the port relationship of the voltage and current terminals of the active element can be rewritten as
The proposed circuit is reanalyzed by taking the tracking errors of the nonideal MODXCCII into account, and the modified current transfer function is given as
Next study is carried on the effect of device parasitics on the performance of the proposed circuit. The various parasitics are a low value parasitic serial resistance
From (
To demonstrate the performance of the proposed circuit, the PSPICE simulation program is used. In the simulation, the TSMC 0.35
Aspect ratios of the transistors.
Transistors 



M_{1}M_{2}  1.4  0.7 
M_{3}–M_{5}  2.8  0.7 
M_{17}M_{18}  2.4  0.7 
M_{19}–M_{21}  4.8  0.7 
M_{6}–M_{16}, M_{22}–M_{28}  9.6  0.7 
CMOS implementation of DXMOCCII.
Simulated gain and phase responses of the allpass filter.
Timedomain input and output responses of allpass filter.
Fourier spectrum of the input and output.
THD variation at output (
In this paper, a new currentmode cascadable allpass filter is presented. The proposed circuit uses single DXMOCCII, a grounded resistor, and a grounded capacitor, which is the minimum component realization for an active RC filter circuit. The circuit requires no matching constraints and low active and passive sensitivities and employs grounded passive components only, which makes it suitable for integrated circuit implementation. The circuit also exhibits the feature of lowinput impedance and highoutput impedance. The PSPICE simulation results of the proposed circuit are in good agreement with the theoretical results.
The authors are thankful to the academic editors for recommending this paper.