ACEEE Int. J. on Electrical and Power Engineering, Vol. 01, No. 03, Dec 2010
Electronically Tunable CurrentMode
SIMO/MISO Universal Biquad Filter Using MO
CCCCTAs
S. V. Singh1, S. Maheshwari2, and D. S. Chauhan3
1Department of Electronics and Communications, Jaypee University of Information Technology,
Waknaghat, Solan173215 (India)
Email: sajaivir@rediffmail.com
2Department of Electronics Engineering, Z. H. College of Engineering and Technology,
Aligarh Muslim University, Aligarh202002 (India)
Email:sudhanshu_maheshwari@rediffmail.com
3Department of Electrical Engineering, Institute of Technology, Banaras Hindu University,
Varanasi221005 (India)
Email:pdschauhan@gmail.com
Abstract This paper presents an electronically tunable
matching conditions. Unfortunately these reported circuits [2
currentmode SIMO/MISO universal biquad filter using multi
23] suffer from one or more of the following drawbacks:
output current controlled current conveyor transconductance
(i). Lack of electronic tunability [23, 1517, 22].
amplifiers (MOCCCCTAs). The proposed filter employs only
(ii). Excessive use of active and/or passive elements [2
two CCCCTAs and two grounded capacitors. The proposed
5, 718, 2123].
configuration can be used as either single input multioutput
(iii). Can not provide completely standard filter functions
(SIMO) or multi (three) input single output (MISO) current
[46, 10].
mode filter. It can realize all five different standard filter
(iv). Can not provide explicit current outputs [46].
functions i.e. lowpass (LP), bandpass (BP), highpass (HP),
(v). Use of floating passive elements [67, 19].
bandreject (BR) and allpass (AP). The circuit enjoys an
(vi). Require minus input current signal and/or double
independent current control of pole frequency and bandwidth.
input current signal to realize AP filter function [19
Both the active and passive sensitivities are no more than
21].
unity. The validity of proposed filter is verified through
In spice of fact that most of these currentmode filters
computer simulations using PSPICE, the industry standard
are either SIMO or MISO. However, the circuit reported in
tool.
refs. [2223] can be used as SIMO as well as MISO current
mode filter from the same configuration but these circuits
IndexTermsCCCCTA, currentmode, universal, biquad,
[2223] uses excessive number of active and passive
filter
components. CCCCTA is relatively new active element [24]
and has received considerable attentions as current mode
I. INTRODUCTION
active element, because its transconductance and parasitic
The currentmode active filter, where information is
resistance can be adjusted electronically, hence it does not
represented by the branch currents of the circuits rather than
need a resistor in practical applications. This device can be
the nodal voltages as of voltagemode active filter, posses
operated in both current and voltage modes, providing
many unique and attractive characteristics over their voltage
flexibility. In addition, it can offer several advantages such as
mode counter parts including small nodal time constant, high
high slew rate, high speed, wider bandwidth and simpler
current swing in the presence of a low supply voltage,
implementation. All these advantages together, its current
reduced distortion and better ESD immunity [1 ]. During the
mode operation makes the CCCCTA, a promising choice for
last one decade and recent past a number of currentmode
realizing active filters [24]. In this paper an electronically
active filters have been reported in the literature [223], using
tunable currentmode SIMO/MISO universal biquad filter
different current conveyors (CCs). These currentmode active
employing two MOCCCCTAs and two grounded capacitors.
filters are broadly classified as SIMO [214, 2223] or MISO
The proposed configuration can be used as either SIMO or
[1521, 2223] currentmode filters. The SIMO currentmode
MISO current mode filter, without change in circuit
filters can realize second order LP, BP, HP, BR and AP
configuration. It can realize all five different standard filter
responses simultaneously, without changing the connection
functions i.e. LP, BP, HP, BR and AP. The circuit enjoys an
of the input current signal and without imposing any independent current control of pole frequency and
restrictive conditions on the input signal. The MISO current
bandwidth. The circuit possesses low active and passive
mode filters can realize all the standard filter function
sensitivity performance. The performances of proposed
through appropriate selection of the signals without any
circuit are illustrated by PSPICE simulations.
36
(c) 2010 ACEEE
DOI: 01.IJEPE.01.03.100
ACEEE Int. J. on Electrical and Power Engineering, Vol. 01, No. 03, Dec 2010
(I +
+
1
I
C s
I
g
in
in 2 )
2
in3
m 2
I
= 
(5)
OUT 1
D(s)
g
I C R s + (I
 I  I )
m 2 [ in3
1
X 2
in3
1
in
n 2 ]
I
=
(6)
OUT 2
D(s)
I
D(s) 


1
C s
I C s
I
g
in (
2 )
in 2
2
in3
m 2
I
=
(7)
OUT 3
D(s)
g
+
+
1R
I
I
C s
I
g
m
X 2 (
1
in
in 2 )
2
in3
m 2
I
=
(8)
OUT 4
D(s)
Figure 1. CCCCTA Symbol
Where
2
D(s) = s C C R
+ sC + g (9)
II.
1
2
X 2
2
m 2
CIRCUIT DESCRIPTION
The CCCCTA properties can be described by the
It can be seen from (7) that proposed filter circuit can be
following equations
used as three input single output (TISO) currentmode filter
and realizes five standard filter functions at current output
V = V + I R , I = I , I
= I , I = g V
IOUT3 which are follow as:
Xi
Yi
Xi
Xi
Zi
Xi
Zi
Xi
O
mi
Zi
(1)
(i). An inverted BP with Iin2 = Iin and Iin3 = Iin1=0.
where Rxi and gmi are the parasitic resistance
at x terminal and transconductance of the ith CCCCTA
(ii). A noninverted HP with Iin2 = 0 and Iin3 = Iin1=
respectively. Rxi and gmi depend upon the biasing currents
Iin.
IBi and ISi of the ith CCCCTA respectively. The schematic
symbol of CCCCTA is illustrated in Fig.1. The
(iii). A noninverted LP with Iin2 = Iin1= 0 and Iin3 =
implementation of MOCCCCTA with CMOS transistors
Iin.
[25] is shown in Fig.2. For CMOS model of CCCCTA
shown in Fig.2, R
(iv). A noninverted BR with Iin1 = Iin and Iin3 = Iin2
x and gm can be expressed as
= 0.
1
R =
(2)
(v). A noninverted AP with Iin1 =Iin2 = Iin and Iin3
X
8 I
= 0.
n B
and
In this design we can note that there are no need of any
component matching conditions, invertingtype input
g = I
(3)
m
n S
current signal(s) and double input current signal(s) to
realize the above standard filter functions. Moreover,
W
above proposed filter circuit can also be used as single
Where = C
(4)
n
n
OX
L
input multioutput currentmode filter if Iin2 = Iin3 =0 and by
taking Iin1as single input current terminal. From (5) to (8)
where n, COX and W/L are the electron mobility, gate
the following current transfer functions can be obtained.
oxide capacitance per unit area and transistor aspect ratio,
respectively.
I
C
 s
OUT 1
2
=
(10)
I
D(s)
1
in
III. PROPOSED FILTER CIRCUIT

The proposed electronically tunable currentmode
I
g
OUT 2
m 2
=
(11)
SIMO/MISO universal biquad filter circuit is shown in
I
D(s)
1
in
Fig.3. It is based on two MOCCCCTAs and two grounded
capacitors. Routine analysis of the proposed circuit yields
2
I
C C R s + g
OUT 3
1
2
X 2
m2
=
(12)
the following current transfer functions.
I
D(s)
1
in
37
(c) 2010 ACEEE
DOI: 01.IJEPE.01.03.100
ACEEE Int. J. on Electrical and Power Engineering, Vol. 01, No. 03, Dec 2010
Figure 2. Implementation of MOCCCCTA using CMOS transistors
Substituting intrinsic resistances as depicted in (2)  (3), it
yields
1
1
1
2
1
2
4
C I
=
(8I I )1
1
S2
4 , Q =
(15)
o
n
B2 S2
C C
C
8I
1
2
2 B2
From (15), by maintaining the ratio IB2 and IS2 to be
constant, it can be remarked that the pole frequency can be
electronically adjusted by IB2 and IS2 without affecting the
quality factor. In addition, bandwidth (BW) of the system
can be expressed by
1
O
BW =
=
(8 I
(16)
n B ) 1
2
2
Q
1
C
Equation (15) shows that the bandwidth can be controlled
by IB2. From (15) and (16) , it is clear that parameter o
can be controlled electronically by adjusting bias current
IS2 with out disturbing parameter o/Q .
IV. NONIDEAL ANALYSIS
Figure 3. Electronically tunable currentmode SIMO/MISO universal
Taking the nonidealities of CCCCTA into
biquad filter
account, the relationship of the terminal voltages and
I
g R C s
currents can be rewritten as follow.
OUT 4
1
m
X 2
2
=
(13)
I
D(s)
1
in
V = V + I R
I = I
I
=  I
Xi
i
Yi
Xi
Xi , Zi
pi Xi , Zi
ni Xi ,
It can be seen from (10) to (13) that inverting BP,
an inverting LP, noninverting BR and noninverting BP
I = g V
O
i mi
Zi
(17)
filter responses are obtained from output currents IOUT1,
IOUT2, IOUT3 and IOUT4 respectively. HP and AP filter Where i =1vi and vi (  vi  <<1) represents the voltage
responses can be easily obtained from the currents IHP=
tracking error from Y to X terminal, and pi =1pi and pi ( 
IOUT2 + IOUT3 and IAP= IOUT1 + IOUT3 respectively. pi  <<1) represents the current tracking error from X to
Obviously, it is a singleinput sixoutputs current mode
+Z terminal and ni =1ni and ni (  ni  <<1) represents the
universal biquad filter. The pole frequency (o), the quality
current tracking error from X to Z terminal and i is the
factor (Q) and Bandwidth (BW) o /Q of each filter can be
transconductance inaccuracy factor from Z to X terminal.
expressed as
The nonideal analysis of the proposed filter in Fig.3 yields
the denominator of the transfer functions as
1
1
2
g
2
1
m2
=
,
C R g
1
X2 m2
=
,
O
BW =
=
o
Q
C C R
2
C
Q
C R
D(s) = s C C R
+ s C + g
1
2
X 2
2
1
X2
1
n
1 2
X 2
1
p
n2
2
2
1
n
n2
2 2 m2
(14)
(18)
38
(c) 2010 ACEEE
DOI: 01.IJEPE.01.03.100
ACEEE Int. J. on Electrical and Power Engineering, Vol. 01, No. 03, Dec 2010
In this case, the o and Q are changed to
1
1
2
g
2
C g R
n 2 2 2 m2
=
n1
2
1 m2
X2
Q =
o
,
(19)
C C R
C
1
2
X2
p1
n 2 2
2
The active and passive sensitivities of the proposed circuit
as shown in Fig.3, can be found as
1
1
o
S
=  , o
S
= ,
(a)
1
C , 2
C ,R
, , ,
X 2
2
2
n 2
2 gm 2
2
o
S
= 0
(20)
n1 ,
p1 , 1 , 1 , gm1
Q
1
Q
1
S
= 
=
Q
= 
, S
, S
1
,
2
C ,
R
,C , ,g
n 2 , 2
2
X 2
1
2
m 2
2
p1
Q
S
=1 Q
=
, S
0
(21)
R
, ,
n1
X 1
1
1
From the above results, it can be observed that all the
(b)
sensitivities are low and no longer than one in magnitude.
V. SIMULATION RESULTS
Pspice simulations are carried out to demonstrate the
feasibility of the proposed circuit using CMOS
implementation as shown in Fig.2. The simulations use a
0.35m MOSFET from TSMC (the model parameters are
given in Table1). The dimensions of PMOS are determined
as W=3m and L=2m. In NMOS transistors, the
dimensions are W=3m and L=4m. Fig.4 Shows the
simulated current gain responses of the LP, BP, BR, HP
(c)
and AP of SIMO configuration of the proposed circuit in
Fig.3. Fig.5 shows the simulated current gain and phase
responses of the LP, BP, BR, HP and AP of MISO
configuration of the proposed circuit in Fig.3. The
proposed filter is designed with IB1=IB2=6A, IS1=
IS2=54.5A and C1=C2=35pf. The supply voltages are
VDD=VSS=1.85V. The simulated pole frequency is
obtained as 333 KHz. The simulation results agree quite
well with the theoretical analysis.
(d)
(e)
Figure 5 Current gain and phase responses of the (a) BP, (b) HP, (c)
LP, (d) BR and (e) AP of MISO configuration of the proposed
Figure 4. Current gain responses of the LP, BP, BR, HP and AP of SIMO
circuit in Fig.3.
configuration of the proposed circuit in Fig.3
39
(c) 2010 ACEEE
DOI: 01.IJEPE.01.03.100
ACEEE Int. J. on Electrical and Power Engineering, Vol. 01, No. 03, Dec 2010
Further simulations are carried out to verify the total
VI. CONCLUSION
harmonic distortion (THD). The circuit is verified by
applying a sinusoidal current of varying frequency and
An electronically tunable currentmode SIMO/MISO
amplitude 20A.The THD are measured at the LP output
universal bquad filter using only two MOCCCCTAs and two
(IOUT2). The THD is found to be less than 5% while grounded capacitors is proposed. The proposed filter offers
frequency is varied from 10 KHz to 150 KHz. The time
the following advantages
domain response of LP output (IOUT2) is shown in Fig.6. It
(i). Simultaneously realizes LP, BP, HP, BR and AP
is observed that 40A peak to peak input current sinusoidal
responses with the single input three output or three
signal levels are possible with out significant distortions.
input single output from same configuration.
(ii). Both the capacitors are grounded and ideal for
integrated circuit implementation.
(iii). Low sensitivity figures.
(iv). Filter parameters o , Q and o / Q are
electronically tunable with bias current(s) of
CCCCTA(s)
(v). o and o / Q are orthogonally tunable.
(vi). No need to use invertingtype input current signals
or double input current signals to realize all five
standard filter functions.
(vii). Availability of explicit current outputs (i.e. high
impedance output nodes) without requiring any
additional active elements.
Figure 6. Time domain input and LP output (I
With above mentioned features it is very suitable to realize
OUT2) waveforms of the
proposed circuit in Fig .3.
the proposed circuit in monolithic chip to use in battery
powered, portable electronic equipments such as wireless
Table 1. 0.35m level 3 MOSFET parameters
communication system devices.
NMOS:
LEVEL=3 TOX=7.9E9 NSUB=1E17 GAMMA=0.5827871
PHI=0.7 VTO=0.5445549 DELTA=0 UO=436.256147 ETA=0
THETA=0.1749684 KP=2.055786E4 VMAX=8.309444E4
KAPPA=0.2574081 RSH=0.0559398 NFS=1E12 TPG=1 XJ=3E7
LD=3.162278E11 WD=7.04672E8 CGDO=2.82E10
CGSO=2.82E10 CGBO=1E10 CJ=1E3 PB=0.9758533
MJ=0.3448504 CJSW=3.777852E10 MJSW=0.3508721
PMOS:
LEVEL =3 TOX = 7.9E9 NSUB=1E17 GAMMA=0.4083894
PHI=0.7 VTO=0.7140674 DELTA=0 UO=212.2319801
ETA=9.999762E4 THETA=0.2020774 KP=6.733755E5
VMAX=1.181551E5 KAPPA=1.5 RSH=30.0712458 NFS=1E12
TPG=1 XJ=2E7 LD=5.000001E13 WD=1.249872E7
CGDO=3.09E10 CGSO=3.09E10 CGBO=1E10 CJ=1.419508E3
PB=0.8152753 MJ=0.5 CJSW=4.813504E10 MJSW=0.5
40
(c) 2010 ACEEE
DOI: 01.IJEPE.01.03.100
ACEEE Int. J. on Electrical and Power Engineering, Vol. 01, No. 03, Dec 2010
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(c) 2010 ACEEE
DOI: 01.IJEPE.01.03.100
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