Circuits and Systems, 2013, 4, 83-88
http://dx.doi.org/10.4236/cs.2013.41013 Published Online January 2013 (http://www.scirp.org/journal/cs)
Universal Current-Mode Biquad Employing Dual Output
Current Conveyors and MO-CCCA with Grounded
Passive Elements
Kasim Karam Abdalla
Department of Electrical Engineering, Engineering Colloge, University of Babylon, Hilla, Iraq
Received May 17, 2012; revised November 6, 2012; accepted November 13, 2012
ABSTRACT
A new universal multiple input multiple output (MIMO) type current-mode biquad employing two dual output current
conveyors (DOCCII), one multiple output current controlled current amplifier (MOCCCA) and four passive grounded
elements is proposed which can realize all the five basic filtering functions namely, low
- pass (LP), high - pass (HP),
band
- pass (BP), band - stop (BR) and all - pass (AP) in current mode from the same configuration. The centre frequency
o

can be set by the passive elements of the circuit and the quality factor is electronically tunable through bias
currents of the MOCCCA. Therefore, the biquad filter has independent tenability for the
o
Q
o

and Q. The active and
passive sensitivities of and
o
o
Qo

are low. The workability of the new configuration has been demonstrated by
PSPICE simulation results based upon a CMOS CCII in 0.35 μm technology.
Keywords: Current-Mode Filters; Current Conveyors; Analog Circuit Design; CMOS Circuits
1. Introduction
Recently, Chunhua, Hiaguang and Yan presented two
new universal multiple input single output (MISO) cur-
rent-mode (CM) biquadatic filters using one MOCCCA,
two grounded capacitors (GC) and two grounded resis-
tors (GR) and realize all the five generic filter responses
in CM (i.e. with current as input and current as output)
[1].
The purpose of this paper is to introduce a new con-
figuration which although uses exactly same number of
active and passive components but in contrast to the cir-
cuit of reference [1] realizes a MIMO-type biquad and
hence, does not require any additional hardware to du-
plicate/invert current inputs which is required in case of
MISO-type filters of [1].
In the literature there are SIMO-type filter circuits
which have three active devices but suffer from the in-
dependent tunability as in [2-5] or have more passive or
active elements as in [4-9]. The circuits in [10-12] need
double inputs and outputs to realize all five generic filters.
The circuit in [13] has two MO-CCCIIs and one DO-
CCCII, the draw back of this circuit is the control cur-
rents oi are temperature dependent. The cir-
cuit in [14] has two MO-CCCIIs and one MOCCCA but
realizes only SIMO-type biquad.
2. The Proposed Configuration
The proposed configuration is shown in Figure 1.
Assuming the CCIIs to be characterized by
,1,2,3Ii
000
100
010
YY
XX
ZZ
I
V
VI

 

 

I
V

 
(1)

 


 

The symbolic notation of MO-CCCA is given in Fig-
ure 2(a), where i represent input, 1oon
I
Iare n out-
puts respectively, and IA and IB denote DC bias currents.
Figure 2(b) is a CMOS realization of MO-CCCA. Here
Ii denotes the input signal; Io1, Io2, Io3 are the three output
currents, respectively.
If the channel lengths of M5-M8 are all n times of that
of M4, and the channel size of M17 is n times that of M18,
namely






54
64 74
84 1718
,
MM
MM MM
MMM M
WL WL
WL WLWL WL
WL WLWLWLn



the output current expressions can be obtained as
12 2
B
o ooni
A
nI
I
II KI
I
  (2)
C
opyright © 2013 SciRes. CS

K. K. ABDALLA
84
II
CC
II
CC
MOCCCA
1
C
io3
R1
2
R
2
C
Y
1
X1
Y
2
X2
i3
i4
A
B
io1
Z1
Z1
Z2
Z2
C1
2
i2
i5
i1Ii
Io1
Io2
Io3
io2
IB IA
Figure 1. The proposed configuration.
MOCCCA
Ii
Io1
Io2
Ion
IB IA
(a)
M
M
M
M
M
M
8
11
1
1
34
5
6
7
M27
M6 M
M
5
2
M1M3
M4
2
M
MMM
910111
1
0
M
MM
M
1
12
78
9
4
M2
M
M2
2
5
6
3
M
MM
22
2
12
VSS
VDD
IA
IB
Iin
I01 I02I03Ion
I2B
(b)
Figure 2. (a) Symbolic notation of MO-CCCA (b) CMOS realization of the MO-CCCA.
where K represents the current gain. It is clear from
Equation (2) that the value of K can be set by IB and IA.
Consider now the following special cases:
2.1. MISO Type:
When 1234 5 are input currents and taking 03
as output current, then a routine analysis of the circuit
reveals the following expression of the output currt
03
i in terms of the five input currend
,,, andiiii ii
en
nts 1234 5
,,, aiiii i:

2
0321 24 1 21351 2
1
iisCCiGGiiisCG


 (3)



where 2
1212 12
1,
s
CCsCG GG
K
 , 11 1GRand
22
1GR.

Then, the various filter responses can be realized from

K. K. ABDALLA 85
the circuit are:
LPF: when (non-inv.) and
.
4in
ii
0
ii
0
ii
12
ii
35
HPF: when and
2in
ii1 ii
345

0
.

BPF: when and 451in 23 iiiiii

 3in ii or

and or
12
ii 45 0ii 5 i in i

and
.
1
ii
234
Notch: when and .
0i
iii
i
5
0i
ii 15
0ii
i0 ii 
24in
ii 13 APF: when 234 and or
and .
ii
in
13
0ii
245in
iiii
2.2. SIMO Type
If 1 is input current, 2345 (open cir-
cuited) then, the various filter responses realized are
given by:
ii
LPF:

12
1GG 

01
1
i
i (4)
HPF: 2
12
1
02
1
i
s
CC

i





 (5)
BPF:

12
1
03
1
i
s
CGi (6)
Notch: 2
01 02
1
1
ii
12 12
s
CC GG
i






 (7)
APF: 2
01 0203
12
1
1
ii i
1112
s
CC s
i
 

CG GG



(8)
The various parameters of the realized filters are given
by
22
11
CR
KCR 
1212 22
11
,,
oo
BW Q
CC RRKC R
  (9)
From Equation (9), the centre frequency o

can be set
by varying R1 without disturbingoo
Q

. The o can
also be set by IB and IA without disturbingo
Q

. Therefore,
the biquad filter has independent tenability for the o

and .
o
From the above, the active and passive sensitivities of
the transfer function are given as
Q
1212
11
,
1,1
2
oooo
oo o
CCRR
QQ Q
K CR
SSSS
SSS


 
22
11
22
oo
QQ
CR
SS
o
(10)
The active and passive sensitivities of

and are
o
Q
found to be in the range 11
2x
S 
1
1.5 V, 1.5 V, 0.5 V,
DD SS
VVV
F, and the circuit,
thus, enjoys low sensitivities.
3. Simulation Results
To verify the validity of the various modes of operation
of the proposed configuration, circuit simulation of the
current mode filters (MISO and SIMO) have been carried
out using the CMOS CCII implementation with multiple
outputs shown in Figure 3 (as in [15], modified from
[16]).
The model parameters of n-channel and p-channel
MOSFETs are given in [17], whereas aspect ratios of the
CCII MOSFETs are shown in Table 1, and aspect ratios
of the MO-CCCA MOSFETs are shown in Table 2.
The CMOS CCII was biased with DC power supply
voltages


20.9 VV and

1f
.

To achieve the MISO type filters with o

MHz
and quality factor of Qo = 1, the component values were
selected


11, 50 μA, 100 μA
AB
KnI I 
1 kΩRR,
12
159 pFCC and 12


. The frequency
responses of LPF, BPF, HPF, Notch and APF (theoretical
and simulation) are shown in Figure 4.
To test the input dynamic range of the proposed filters,
the simulation of the band-pass filter as an example has
VSS
Z- Z+ X Y
VDD
1
2
4
3
0
M
M
MM
MMMM
M MMMM
M
MMM
MMM
MM
M MM
M
M
M
12
34
56
8
910
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
3
4
5
6
78
9
12
V
V
2
1
5
6
7
8
7
Figure 3. CMOS realization of the CCII.
Table 1. Aspect ratios of CCII MOSFETs.
MOS transistors W/L
M1 - M4 10/0.35
M5, M6 16/0.35
M7, M8 , M13 - M16, M21 - M24, M27, M28 16/0.35
M9 - M12, M17 - M20, M25, M26 30/0.35
Table 2. Aspect ratios of MO-CCCA MOSFETs.
MOS transistors W/L
M1 - M3 9.5/0.55
M4 - M8, M17, M18, M24 - M27 27.5/1.5
M10 - M15, M21 - M23 9.5/1.35
M16, M19, M20 4.5/0.7

K. K. ABDALLA
86
10
5
10
6
10
7
-60
-50
-40
-30
-20
-10
0
10
Frequency (Hz)
Gain (dB )
LP Theoretical
HP Theo retical
BP Theoretical
BR Theoretical
LP Simulatio n
HP Simulation
BP Simulation
BR Simulation
(a)
10
5
10
6
10
7
-50
-40
-30
-20
-10
0
10
20
30
40
50
Frequency (Hz)
Gain (dB )
AP si mulation
AP Theoreti cal
p
hase
(
de
g
ree
)
-400
-350
-300
-250
-200
-150
-100
-50
0
P has e simul ati on
P has e Theoreti c al
(b)
Figure 4. PSPICE Simulation results (a) Gain response of
LPF, BPF, HPF and Notch; (b) Gain and Phase response of
APF.
been done for a sinusoidal input signal at o1 MHzf

.
Figure 5 shows that the input dynamic range of the filter
response extends up to amplitude of 105 μA without sig-
nificant distortion. The dependence of the output har-
monic distortion on the input signal amplitude is illus-
trated in Figure 6. For input signal amplitudes lower
than 110 μA, the total harmonic distortion (THD) is of
the order of less than 1% after that rapidly increasing is
occurred. The obtained results show that the circuit oper-
ates properly even at signal amplitudes of about 120 μA
and THD less than 4%.
To achieve the SIMO type filters with o1f

MHz
and quality factor of , the component values were
selected ,
12 and 12
CC . The circuit real-
izes LP, HP, and BP responses, respectively, at 0102
03 simultaneously. The frequency responses of
Notch and AP can be realized by, respectively,
Figure
Figure 8 shows th
2
o
Q

100 μAI
;ii
filter responses are
shown in 7.
e simulation results for control of Qo
w
able 3. Figure 9
21,KnI
RR
and
01
ii

01 02 03
iii
25 μA,
AB
159 pF
. Four
1 kΩ
i

02 and
hile keeping fo fixed (1MHz) with 12
159 pFCC
for different values of Qo as shown in T
shows the simulation results for control of fo while keep-
ing Qo = 1 with 12 53 pFCC

 for different values of
fo as shown in Ta nt mode band pass filter ble 3. The curre
88.2 8.4 8.6 8.8 99.2 9.4 9.6 9.810
x 10
-6
-1.5
-1
-0.5
0
0.5
1
1.5 x 10
-4
Tim e ( s)
Ampl it ude (A)
Iin
Io3
Figure 5. Time domain response of the input and output
waveforms of the band-pass filter of the proposed circuit
for 1 MHz sinusoidal input current of 105 μA.
7
0
1
2
3
4
5
6
5102030405060708090
100 105 110 120 130
Iin (uA)
THD %
Figure 6. Dependence of output current harmonic- distor
tion on input current amplitude of the band-pass filter of
proposed circuit.
10
0
-10
-20
-30
10
5
10
6
10
7
-60
-50
-40
Frequency (Hz)
Gain (dB )
LP Theoretical
HP Theoretical
BP Theoretical
BR Theoretical
LP Simulation
HP Simulation
BP Simulation
BR Simulation
Figure 7. PSPICE Simulated gain responses of LP, BP, HP
and Notch for SIMO type filter.

K. K. ABDALLA 87
Table 3. The R1 and R2 values for controlling of Qo
and C and C values for cont
1 2rolling fo.
Fixed fo Fixed Qo
Qo 2 kΩ MHz R2 kΩ
R1 kΩ Rfo R1 kΩ
1 1 1 3 3
1.43
1
2 0.7 2 1.5 1.5
4 0.5 2 3 1 1
10
5
10
6
10
7
-30
-25
-20
-15
-10
-5
0
Frequen c y (Hz)
Gain (dB )
Qo = 1
Qo = 2
Qo = 4
Q
o
= 1
Q
o
= 2
Q
o
= 4
Figure 8. Simulation results for control of Qo while keeping
f fixed (1 MHz) for band pass filter.
o
10
5
10
6
10
7
-30
-25
-20
-15
-10
-5
0
Frequenc y (Hz )
Gain (dB )
fo =1 MHz
fo =2 MHz
fo =3 MHz
f
o
= 1 MHZ
f
o
= 2 MHZ
f
o
= 3 MHZ
Figure 9. Simulation results for control of fo while keeping
Q (=1) fixed for band pass filter.
tor tuning while keeping
RR
ine 10
o
is tested for gain and quality fac
pole frequency constant at 1 MHz. 12 1 kΩ,
12
159 pFCC and 1,2,4K are taken for gain =
quality factor 1, 2, 4, respectively. The simulated re-
sults are shown Figur .
A very good correspondence between design values
and values determined from PSPICE simulations is ob-
served, which confirms the workability of the current
mode filters realized from the proposed configuration.
10
5
10
6
10
7
-25
-20
-15
-10
-5
0
5
10
Frequecy (Hz )
Gain (dB)
Qo=K=0.5
Qo=K=0.71
Qo=K=1
Qo=K=2
Q
o
= K = 0.5
Q
o
= K = 0.71
Q
o
= K = 1
Q
o
= K = 2
Figure 10. Simulation results for control of Qo and gain
while keeping fo = 1 MHz fixed for band pass filter.
type current-mode biquad
OCCCA and four passive
4. Concluding Remarks
A new universal MISO/SIMO
employing two DOCCII, one M
grounded elements is proposed in this paper. The purpose
of this paper as to introduce a new configuration which
although uses exactly same number of active and passive
components but in contrast to the circuit of reference [1]
realizes a MIMO-type biquad and hence, does not require
any additional hardware duplicate/invert current inputs
which is required in case of MISO-type filters of [1]. The
centre frequency o

can be set by the passive elements
of the circuit and the quality factor o Q is electronically
tunable through b currents of the MOCCCA. There-
fore, the biquad filter has independent tenability for the
o
ias

and o Q. The active and passive sensitivities o Q
and o

are low.
The workability of the new configuration has be
demotrated by PS
en
nsPICE simulation results based upon a
C
S
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