Circuits and
S
doi: 10.4236/c
s
Copyright ©
2
Nt
h
Abstract
This paper p
r
controlled c
u
pology can i
m
ters offer th
e
(CCCIIs) an
external resi
0.35 µm C
M
provided. T
h
Keywords:
A
1. Introdu
c
N
owadays, c
u
the realizatio
n
cuits and sys
t
formance pro
p
dynamic rang
chip area [1
,
conveyor (C
C
whereas sec
o
conveyor (C
C
adjustability
o
b
ias current
[
dratic filters
h
cited there in.
b
ly used to r
e
hence serves
filters can be
cading of lo
w
or signal flo
w
veyor (CCII
o
[10-14] and
v
p
orted. As th
i
mode filters,
ready reporte
d
are made in
T
Sy
stems, 2011
s
.2011.22013 P
u
2
011 SciRes.
h
Orde
r
Cu
r
Depart
m
Receiv
e
r
oposes an n
t
u
rrent conve
y
m
plement b
o
e
following i
m
d passive c
o
stor suitable
M
OS technol
o
h
e results are
A
nalog Filter
s
c
tion
u
rrent convey
o
n
of various
a
t
ems. They ar
p
erties such a
s
e, low power
,
2]. The basi
c
C
II) does not
h
o
nd generatio
n
C
CII) possesse
o
f intrinsic res
i
[
3-5]. Alread
y
h
ave been rep
However, th
e
e
alize any hig
h
a wide range
obtained by
v
w
er order filte
r
w
graph. Alre
a
o
r CCCII) bas
e
v
oltage mode
i
s paper is co
n
hence only th
d
higher orde
r
T
able 1.
, 2, 85-90
u
blished Online
r
Volta
g
r
rent
C
m
ent of Electr
o
E-mai
l
e
d January 4,
2
t
h order (wh
e
y
ors (CCCIIs
o
th band pas
s
m
portant fea
t
o
mponents, n
for integrati
o
o
gy. PSPICE
found to agr
e
s
, Active-C
F
o
rs play an i
m
a
nalog signal
e accepted to
s
wide signal
b
consumption
a
c
second ge
n
h
ave in built
t
n
current co
n
s this propert
y
i
stance at port
y
a number o
f
orted in [6-9]
e
nth order fil
t
h
er order filte
r
of applicatio
n
v
arious metho
r
s or state va
r
a
dy a number
e
d higher ord
e
[15-18] filter
s
n
cerning high
e
h
e study of th
e
r
voltage mod
e
April 2011 (htt
p
g
e Mo
d
C
ontroll
Ashish Ra
n
o
nics Enginee
r
l
: {ashish.ism,
2
011; revised
F
er
e n = 2,3,

) and n num
b
s
and low pa
s
t
ures: use of
o matching
c
o
n, cu
t
off f
r
simulation r
e
e
e well with
t
F
ilter, Higher
m
portant role f
o
processing c
i
have high pe
b
andwidth , hi
g
a
nd occupy le
s
n
eration curre
n
t
uning propert
y
n
trolled curre
n
y
because of t
h
X of CCCII
b
f
analog biqu
a
and
r
eferenc
e
t
er can be fle
x
r
function a
n
n
s. Higher ord
e
ds such as ca
r
iable techniq
u
of current co
n
e
r current mo
d
s
have been
r
e
e
r order volta
g
e
features of
a
e
filters [15-1
8
p
://www.SciRP.
d
e Activ
l
ed Cu
r
n
jan, Sajal
K
r
ing, Indian S
c
sajalkpaul}
@
F
ebruary 21,
2

, n) voltage
m
b
er of equal
v
s
s responses
w
minimum n
u
c
onstraint, u
s
r
equency ca
n
e
sults of thir
d
t
he theory.
Order Volta
g
o
r
i
r-
e
r-
g
h
s
s
n
t
y
,
n
t
h
e
b
y
a
-
e
s
x
i-
n
d
e
r
s-
u
e
n
-
d
e
e
-
g
e
a
l-
8
]
In t
h
order (
w
p
ass a
n
same t
o
tors. It
p
ology
p
leme
n
electro
n
2. Ci
r
The ci
r
1 The
p
where,
and a
n
R
X
, the
X
p
ort
CCCII
org/journal
/
cs)
e-C Fil
t
r
rent C
o
K
. Paul
c
hool of Mines
,
@
rediffmail.co
m
2
011; accepte
d
m
ode active-
C
v
alued grou
n
w
ithout alter
a
u
mber of cur
r
s
e of all gro
u
n
easily be el
e
d
order ban
d
g
e Mode Filt
e
h
is work, an a
t
w
here, n = 2,3
n
d band pass
r
o
pology usin
g
does not re
q
is an active-
C
n
tation. The u
s
n
ic tunability
[
r
cuit Descr
i
r
cuit symbol
o
p
ort relationsh
i
0
YX
I
, V

the positive
a
n
egative DO
C
intrinsic seri
e
is electronical
shown in Fi
gu
x
R
mi
g

i
β
t
er Em
p
o
nveyo
r
,
Dhanbad,
I
n
d
m
d
March 7, 20
1
C
filter using
n
ded capacit
o
a
tion of any
c
r
ent controll
e
u
nded capac
i
e
ctronically
a
d
pass and lo
w
e
r, CCCII
t
tempt is mad
e
,,n) voltag
e
r
esponses can
g
n CCCIIs a
n
q
uire any resi
s
C
filter and
h
s
e of CCCIIs
[
5] of the filte
r
i
ption
o
f the DOCC
C
i
p of a DOCC
C
YXX
VI|R |,


a
nd negative
s
C
CCII respect
i
e
s input resist
a
l
y tunable via
u
re 2 and R
X
m
24mm
1
gg


0
2
2
i
βI i
0ins ii
ox i
εε μW
tL

p
loyin
g
r
d
ia
1
1
n number o
f
o
rs. The prop
o
c
omponents.
e
d current co
n
i
tors and ab
s
a
djusted usi
n
w
pass respo
n
e
to propose a
e
mode filter.
B
be obtained
f
n
d grounded
n
s
tor. The pro
p
h
ence ideal fo
r
in the circuit
p
r
parameters.
C
II is shown i
n
C
II can be de
f
ZX
I I

s
igns define a
i
vely. In this
a
nce of the co
n
I
0
of the CM
O
m
ay be define
d

2
4,
CS
g
f
current
o
sed
t
o-
The fil-
n
veyors
s
ence of
n
g AMS
n
ses are
new nth
B
oth low
f
rom the
n
capaci-
p
osed
t
o-
r
IC im-
p
rovides
n
Figure
f
ined as
(1)
positive
equation
n
veyor at
O
S based
d
as [5]
(2)
(3)
(4)

86 A. RANJAN ET AL.
Table 1. Comparative study of the available nth order voltage mode filter.
Ref. No.
Active
element used
and number of
active
elements
required
Number of
capacitors required
Number of
resistors required
All passive
elements are
grounded
In built tunability
of filter
parameters
Types of filter
implemented
Require to
change the
hardware to
change filter
type
15 CCII, 3n–2 n+1 3n–1 Yes No Universal filter Yes
16 CCII, n+1 n n+2 No No Low pass Not
Applicable
17 CCII, n+2 Minimum 2n+3 No No Universal filter Yes
18 CCCII, n+1 n 1 Yes Yes Low pass Not
Applicable
Proposed CCCII, n n Nil Yes Yes Low pass &
Band pass No
Figure 1. Block dia gram of DOCCCII .
where, gm2 and gm4 are the transconductances of M2 and
M4 respectively, I0 is bias current of DOCCCII. The
proposed voltage mode nth order filter circuit is shown in
Figure 3.
The routine analysis of the circuit of Figure 3 gives
the transfer function for an nth order filter as

12inin x
out
VsVRC
VDS

 (5)
where





2
10
1anj
n
nn nnj
nnxxn xn
nn j
j
DS
aRCsRCsaRC sa









(6)
23 ,n,,n (7)
1
nn
a (8)
 
1nnjnjnj njnj
aa a

 (122j,,,n)
(9)
12 n
a (10)
01 n
a (11)
From above equations we can see that specialization in
the numerator of (5) results in the following filter res-
ponses:
1) Low pass Response
 At out V with1iin n VV

and 20
in
V
2) Band pass Response
 At out V with 10
in
V

and 2in in VV
Hence, the proposed circuit gives an inverted nth order
band pass filter and nth order low pass filter from the
same topology.
As an example, a third order transfer function
12
333 222
321
inin x
out
xxx
VsVRC
VsRC sRCsRC




(12)
is realized using (5)–(11) and the corresponding third
order circuit obtained from the nth order circuit of Fig-
ure 3 is given in Figure 4.
With 1in in
VV

and, Equation (12) simplifies to
333 222
x321
in
out
xx
V
VsRC sRCsRC 


(13)
which is a low pass response.
Similarly, within1 V0

and, Equation (12) simplifies
to
333 222
321
in x
out
xxx
sVR C
VsRC sRCsRC




(14)
which is a band pass response.
The forth order filters is obtained by adding section
shown in Figure 5 between 2nd and 3rd CCCII- of Figure
4. Similarly, fifth and higher order filters are obtained by
adding one section shown in Figure 5 for each higher order.
Comparision of the available nth order filters [15-18]
and the proposed one is given in Table 1. It reveals that
the proposed circuit uses minimum number of current
conveyors and passive components and no resistor. It can
realize both band pass and low pass responses in contrast
to only low pass response in [16,18] and does not require
to change any hardware to change filter type. The uni-

A. RANJAN ET AL. 87
Figure 2. Internal structure of DOCCCII.
Figure 3. Proposed voltage mode nth or de r low pass and band pass filters.
Figure 4. Proposed voltage mode third order low pass and
band pass filters.
versal filters realized by structures in [15,17] are attrac-
tive, but the changing of the filter type would required
the change of hardware of the filter circuits. Hence they
are not suitable for monolithic IC implementation.
3. Simulation and Results
To verify the theory, the proposed voltage mode nth or-
Figure 5. Section to be added for higher order filter.
der filter circuit is simulated with PSPICE using 0.35 µm
AMS CMOS based CCCII circuit given in Figure 2 [5]
with supply voltage of ±2.5 volts and aspect ratio of
transistors as given in Table 2.
As an example, a third order low pass filter and a band

A. RANJAN ET AL.
88
Table 2. MOS dimensions used in the circuit.
Transistors W(µm) L(µm)
M1, M2 20 0.35
M3, M4 60 0.35
M5, M6, M7 30 2
M8, M9 10 2
M10, M11, M14, M15 10 1
M12, M13, M16, M17 30 1
pass filter are obtained with C = 50 pF and I0 = 200 µA.
Frequency responses of the proposed low pass and band
pass filters are shown in Figure 6 and Figure 7 respec-
tively. The response for the low pass filter exhibits a
–60 dB/dec slope for frequencies higher than f0. The re-
sponse for the band pass filter, as shown in Figure 7,
exhibits an asymmetrical third order nature with a slo pe of
20 dB/dec for frequencies lower than f0 and -40 dB/dec
for frequencies higher than f0. The results show a close
matching with the theoretical values. The deviation at
higher frequency may be due to parasites of DOCC-
CII/CCCIIs. The time-domain response of the band pass
filter is shown in Figure 8. Large signal behavior of the
proposed filter is investigated by observing the depen-
dence of the output total harmonic distortion (%THD)
upon the level of input sign al. The result as illustrated in
Figure 9, shows that the %THD is well within the rea-
sonable limit of 4% [19] for input peak-to-peak voltage
level of 2 V. Responses as shown in Figures 8 and 9
reveal that the output is of good quality.
4. Conclusions
In this paper a generalized nth order (where n = 2,3,,n)
voltage mode active-C filter topology is proposed. Both
nth order band pass and low pass responses may be rea-
lized using same topology. The topology uses n equal
value grounded capacitors, single dual output current
controlled current conveyor (DOCCCII) and (n-1) cur-
rent controlled current conveyors (CCCIIs). The verifi-
cation of the theory is performed by using AMS 0.35 µm
CMOS based DOCCCII/CCCII. Comparison with the
reported publications [15-18] reveals that the proposed
topology uses minimum number of active analog build-
ing blocks and minimum passive components. All of the
used capacito rs are grounded. I t does not u se any resistor
and there is no requirement of changing any hardware for
changing filter type from low pass to band pass or
Figure 6. Frequency response of the third order low pass filter.
Figure 7. Frequency response of the third order band pass filter.

A. RANJAN ET AL.
89
Figure 8. Time response of the band pass filter for input peak-to-pea k voltage of 2 V.
Figure 9. %THD verses input voltage at 10 MHz.
vice-versa, hence suitab le for monolithic IC implementa-
tion.
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