Circuits and
S
doi:10.4236/cs.
Copyright ©
2
Thir
d
Abstract
A novel cur
r
tance Ampli
pass and hi
g
mance facto
r
electronicall
y
From sensiti
v
respect to th
e
tave. The pr
o
Keywords:
C
1. Introdu
c
In recent yea
r
circuit techni
q
high accurac
y
p
licity of imp
l
of current m
o
as OAs, OT
A
reported in th
linear electro
n
transconduct
a
resistors; hen
c
tion.
Recently, t
h
used for real
i
Tsukutani et
b
iquad filter
u
grounded cap
a
This paper
third order ac
t
structed with
shown that th
e
function, and
tronically tun
e
The proposed
Sy
stems, 2010
2010.12011 Pu
b
2
010 SciRes.
d
Orde
r
Received
r
ent mode a
c
fiers (OTAs
)
g
h pass filter
r
s natural fr
e
y
tunable. T
h
v
ity analysis
e
circuit acti
v
o
posed circu
i
C
urrent Mod
e
c
tion
r
s, current mo
d
q
ues have rece
y
, the wide si
g
l
ementing sig
n
o
de circuits e
m
A
s, and curren
t
e literature [2
-
n
ic tunability
a
a
nce gain.OT
A
c
e they are s
u
h
e multiple c
u
i
zing current
m
al. proposed
u
sing multiple
a
citors.
focuses on re
t
ive-only filte
r
OAs and du
a
e
circuit can r
e
that the circu
e
d by the tran
s
circuit enjoys
, 1, 65-70
b
lished Online
O
r
Curr
e
O
1
I
ndira Ga
n
2
Dnyan
a
August 5, 201
c
tive-only u
n
)
and three
O
characteristi
e
quency (ω
0
)
h
e proposed
c
, it has been
v
e elements.
i
t facilitates i
n
e
Filter, OTA
d
e analogue si
ived wide att
e
g
nal bandwid
t
n
al operations
m
ploying acti
v
t
conveyors (
C
-
6]. An OTA
p
a
nd wide tun
a
A
based circ
u
u
itable for mo
n
u
rrent output
O
m
ode filters [
good versatil
e
current outpu
t
alization of t
h
r
. The propose
a
l current out
p
e
alize the biq
u
it characterist
i
s
conductance
the features o
O
ctobe
r
2010 (
h
e
nt Mo
d
O
p.am
p
G. N. Shind
n
dhi (SR) Col
l
sadhana Coll
e
s
hi
n
0; revised Se
p
n
iversal filter
O
perational
A
c
s by choosi
)
, bandwidth
(
c
ircuit has v
e
clearly sho
w
The gain rol
n
tegrability,
p
, Bandwidth,
gnal processi
n
e
ntion due to t
h
t
h and the si
m
[1]. The desi
g
v
e devices su
c
C
Cs) have be
e
p
rovides a hi
g
a
ble range of
i
u
its requires
n
n
olithic integ
r
a
O
TAs have be
e
7-12]. In 199
6
e
current mo
d
t
OTAs and t
w
h
e curren
t
-mo
d
d circuit is co
n
p
ut OTAs. It
u
adratic trans
fe
i
cs can be ele
c
gains of OT
A
f:
h
ttp://www.Sci
R
d
e Uni
v
p
. and
O
d
e
1
, D. D. M
u
l
ege, Nanded,
M
e
ge, Thane,
Ma
n
o
p
tembe
r
8, 201
using four
d
A
mplifiers (
O
ng the suita
b
0
(
)
Q

, qualit
y
e
ry low sensi
t
w
n that the p
r
l-off of high
p
rogrammab
i
Center Freq
u
n
g
h
e
m
-
g
n
c
h
e
n
g
h
i
ts
n
o
a
-
e
n
6
,
d
e
w
o
d
e
n
-
is
fe
r
c
-
A
s.
 s
a
 r
e
 d
e
design
 h
i
 e
l
curren
t
 i
n
gains,
 l
o
2. Ci
r
Tr
e
The o
p
known
where
A
0

:
A
0
ω
For
S
R
P.org/journal/c
s
v
ersal
F
O
TAs
u
lajkar
2
M
aharashtra,
a
harashtra, I
n
o
.co.in
0; accepted S
e
d
ual current
o
O
As) is prese
n
b
le current o
u
y
factor Q a
n
t
ivities with
r
r
oposed circ
u
pass and lo
w
i
lity and eas
e
u
ency, Circu
i
a
ving in comp
o
e
alization of v
a
e
void of resis
techniques,
i
gh impedanc
e
l
ectronic adju
s
t
s of the active
n
dependent e
l
o
w sensitivity
f
r
cuit Anal
ys
e
atment
p
en loop gain
o
first order po
l
A
A
0:
Open loop
Open loop – 3
0
: β
i
= gain-
ba
S
>> ω
0
s
)
F
ilter U
s
India
n
dia
e
ptembe
r
15,
2
o
utput Oper
a
n
ted. The ci
r
u
tput branch
e
n
d transcond
u
r
espect to cir
u
it has very l
o
w
pass confi
g
e
of impleme
n
i
t Merit Fact
o
o
nents,
a
rious filterin
g
tors and cap
a
e
outputs,
s
tment of ω
0
a
elements
l
ectronic adj
u
f
igures.
s
is and An
a
o
f an OA is r
e
l
e model [13-1

0
0
A
A
SS



D.C. gain of
o
dB bandwidth
a
ndwidth
p
rod
u
s
ing O
n
2
010
a
tional Trans
c
r
cuit can rea
l
e
s. The filte
r
u
ctance gain
cuit active e
l
o
w sensitivit
i
g
uration is 1
8
n
tation.
o
r Q
g
responses,
a
citors which
a
nd
0
Q

thro
u
u
stment of
p
a
l
y
tical
e
presented by
5]
0
0

o
p-amp.
of the op-am
p
u
ct of op-amp
.
CS
n
ly
c
onduc-
l
ize low
r
perfor-
gm are
l
ements.
i
es with
8
dB/oc-
suits IC
u
gh bias
p
assband
the well
p
= 2 пf
0
.

G. N. SHINDE ET AL.
66

0i 0
(i1,2,3,)
A
AS SS


This model of OA is valid from a few kHz to few
hundred kHz. In this frequency range, OTA works as an
ideal device. The OTA is characterized by the port-rela-
tion
IO = gm (V+ - V-)
where, gm is transconductance of OTA. In the dual cur-
rent output OTA, the plus current output has a positive
polarity, and the minus current output has a negative
polarity.
The analysis gives the current transfer function T = [I
out / I in] as follows:
T(S) =
2
01122212 3233123
2
01122 2
3
1232331 3
3
2
)(()
())(
mbmb mbmbmbmb
mama mamamama
gggSg gg
g
SS
SSggSg gg




 


 (1)
The circuit was designed using coefficient matching
technique. i.e., by comparing these transfer functions
with general third order transfer functions is given by,
T(S) =
00
32
210
32
3
22
0
11
(1 )(1 )
SSS
SS S
QQ




 
(2)
Comparing Equations (1) with (2) we get,
0
31
323
0
ma
ma
g
g


  0
12
212
0
1
(1 ) ma ma
ma
gg
gQ




 (3)
212323
0
0
1
(1 ) mb mb
ma
gg
Qg





0
3
0
mb
ma
g
g
  And 3
0
0
mb
ma
g
g
 
It is found from above equations that circuit parame-
ters ω0, Q; α0 can independently set and electronically
tuned adjusting the transconductance gains of the OTAs.
If 0ma
g
,1

, 2

and 3

are given, the parameter ω0
can be set by 2ma
g
. The parameters Q and α3 can be set
by 1ma
g
and 0mb
g
respectively. It seems that the values
of Q and α3 are also limited by the dynamic ranges of the
OA and OTA.
From (1), it can be seen that:
1) The low pass transfer function can be realized with
00 mb
g

112 2mb mb
gg



and 212 323mb mb
gg

 
2) The high pass transfer function can be realized with
30 mb
g

112 2mb mb gg



and 212 323mb mb gg

 
3) The band pass transfer function can be realized with
30
0
mb mb
gg

112 2mb mb
gg



The high pass and low pass transfer functions obtained
are as follows,

3
0
32
011 22212 3233123
()
HP
mama mamamama
S
TgS ggSggSg


  


3
32
01122212 3233123
()
LP
mama mamamama
TgS ggSggSg


  

The realization of the other transfer functions invariably
requires matching the conditions in terms of the tran-
sconductance gains of the OTAs and the gain-bandwidth
products of the OAs.
The transconductance gains of the OTAs to realize the
desired characteristics are obtained from (3) as
3
0123
3
0
ma
ma
gg



2
000
2
12 123
1
{1 }
ma
ma
g
gQ








00 22
1
11
1
1
ma ma
ma
gg
gQ







where ω0, Q, , ,  and  should be given in
advance.
Methods of implementing a dual current output OTA
have been discussed previously (Ramirez-Angulo et al.
1992, Wu 1994).
3. Circuit Diagram
The diagram was shown in Figure 1.
4. Circuit Description
The proposed circuit is built with four dual current out-
put OTAs and three OAs is as shown in Figure (1). The
V+ terminal of first OTA and V-terminal of all other
OTAs are grounded. Output terminal of first OTA carry-
ing positive polarity current is fed to inverting terminal
of first OA. Its output is fed to inverting terminal of

G. N. SHINDE ET AL. 67
Figure 1. Circuit diagram of electronically tunable third order current-mode universal filter.
non-inverting of third OA output of third OA is then fed
to v+ terminal fourth OTA. Output terminals of all OTAs
carrying positive current are fed to inverting of first OA
whereas remaining current output terminals of all OTAs
adds to give output current of the circuit. The circuit can
realize various third order filter functions by suitably
choosing the current output branches.
5. Result and Discussion
The circuit performance is studied for Central frequen-
cies f0 = 100 kHz and 1 MHz with circuit merit factor Q
= 1. The general operating range of this filter is 10 Hz to
1 MHz. The value of 123

 = 6.392 × 106 for LF
356 N. The proposed circuit gives response only for very
high frequencies since the values of transconductance of
OTAs takes very low values at frequencies less than 100
kHz. The values of 12 ,
ma ma
g
gand 3ma
g
are calculated by
taking 0ma
g
= 2 and 3
0
1
ma
ma
g
g Response is studied for
Q = 1 for high pass and low pass function. Figures 2 and
3 shows high pass and low pass response of the proposed
filter circuit respectively. Data obtained after analysis
high pass and low pass response is given in Tables 2 and
3. From Figures 2 and 3, it is seen that the gain roll-off
is 18 dB/octave for both the functions and the gain stabi-
lizes to 0 dB at frequency 200Hz. There is no overshoot
in the response. Observed - 3 dB frequency i.e. cutoff
frequency matches with designed value f0. Thus the filter
circuit works ideal for high pass as well as low pass
function. The values of transconductance gains for f0 =
100 kHz and 1 MHz obtained are given in Tables 1(a)
and (b) respectively.
6. Sensitivities
The practical solution is to design a network that has low
sensitivity to element changes [14,15]. Thus sensitivity
must be less than limit i.e. unity. The lower the sensitiv-
ity of the circuit, the less will its performance deviate
because of element changes. The sensitivities 0
x
S

and

G. N. SHINDE ET AL.
68
3
x
S

with respect to the circuit active elements are
shown in Table 4. These values are within the range
01
y
x
S
It is found that the proposed circuit has very
low sensitivity with respective to active elements.
7. Concluding Remarks
A versatile current-mode active-only filter using OAs
and OTAs has been proposed. The proposed circuit can
1k10k 100k1M10M
-70
-60
-50
-40
-30
-20
-10
0
10
20
F100kHz
F1MHz
GAIN(dB)
FREQUENCY(Hz)
Figure 2. High pass response of proposed current-mode filter.
1001k10k 100k1M10M
-70
-60
-50
-40
-30
-20
-10
0
10
F100kHz
F1MKz
GAIN(dB)
FREQUENCY(Hz)
Figure 3. Low pass response of proposed current-mode filter.
FREQUENCY (Hz)
GAIN (dB)
F100kHz
F1MHz
FREQUENCY (Hz)
F100kHz
F1MKz
GAIN (dB)

G. N. SHINDE ET AL. 69
Table 1. The values of transconductance gains.
ma
g
Value in mS for f0 = 100 kHz
0ma
g 2
1ma
g
0.356
2ma
g 0.0367
3ma
g 0.0019
0mb
g 2
3mb
g 0.0019
(a) for f0 = 100 kHz
ma
g
Value in mS for f0 = MHz
0ma
g 2
1ma
g
1.966
2ma
g 1.965
3ma
g 1.9
0mb
g 2
3mb
g 1.9
(b) for f0 = 1 MHz
Table 2. Analysis of frequency response of high pass func-
tion for Q = 1.
f0
(kHz)
FOH
(kHz)
f0  FOH
( kHz )
Gain Roll-off in
stop band
Gain Stabi-
lization
dB/Octave
Octave
starting at
( kHz )
dB FS
(kHz)
100 100 0 18 500 0
1 M 1 M 0 18 500 0 2 M
FOH: –3 dB Frequency FS: Frequency at which gain stabilizes
Table 3. Analysis of frequency response of low pass func-
tion for Q = 1.
f0
(kHz)
FOL
(kHz)
f0  FOL
( kHz )
Gain Roll-off in
stopband
Gain Stabili-
zation
dB/Octave
Octave
starting
at
( kHz )
dB FS
(Hz )
100 100 0 18 400 0 100
1M 1M 0 18.3 2 M 0 100
FOL: –3 dB Frequency
realize the biquadratic transfer function and the circuit
characteristics can be electronically tuned by the tran-
sconductance gains. From sensitivity analysis, it has been
clearly shown that the proposed circuit has very low sen-
sitivities with respect to the circuit active elements.
Table 4. Sensitivities 0
x
S

and 3
x
S

.
The gain roll-off of high pass and low pass configura-
tion is 18dB/octave.
8. References
[1] T. Tsutani, T. Higashimura, Y. Sumi and Y. Fukui,
“Electonically Tunable Current Mode Active Only Biqu-
adratic Filter,” International Journal of Electronics, Vol.
87, No. 3, 2000, pp. 307-314.
[2] C.-C. Hsu and W.-S. Feng, “Dynamic Decoupling and
Compensating Methods of Multi-Axis Force Sensors,”
International Journal of Electronics, Vol. 88, No. 1, 2001,
pp. 41-51.
[3] I. A. Khan and M. H. Zaidi, “Multifunction Translinear-C
Current – Mode Filter,” International Journal of Elec-
tonics, Vol. 87, No. 9, 2000, pp. 1047-1051.
[4] M. Higashimura, “Current Mode Low Pass and Band
Pass Filters Using the Operational Amplifier Pole,” In-
ternational Journal of Electronics, Vol. 74, No. 6, 1993,
pp. 945-949.
[5] T. M. Ishida, Y. Fukui and S. Tsuiki, “Novel Electroni-
cally Tunable Current Mode Filter without External Pas-
sive Elements,” IEEE, Vol. 1, 1996, pp. 262-265.
[6] G. W. Roberts and A. S. Sedra, “A General Class of Cur-
rent Amplifier Based Biquadratic Filter Circuits,” IEEE
Transactions on Circuits and Systems, Vol. 39, No. 4,
1992, pp. 257-263.
[7] J. Ramirez-Angulo, M. Robinson and E. Sanchez-Sinen-
cio, “Current Mode Continuous Time Filters Two Design
Approaches,” IEEE Transactions on Circuits and Systems,
Vol. 39, No. 6, 1992, pp. 337-341.
[8] N. A. Shah, M. F. Rather, M. A. Malik and S. Z. Iqbal,
“Cascadable Electronically Tunable Sito Current Mode
Active Only Universal Filter,” ETRI Journal, Vol. 26,
2004, pp. 295-300.
[9] A. K. Mitra and V. K. Aatre, “Low Sensitivity High-
Frequency Active R Filters,” I.E.E.E. Transactions on
Circuits and Systems, Vol. 23, No. 11, 1976, pp. 670-
676.
[10] G. N. Shinde and P. B. Patil, “Sadhana,” Journal of En-
gineering Science, Vol. 28, No. 6, 2003, pp. 1919-1926.
[11] T. Tsukutani, M. Higashimura, Y. Sumi and Y. Fukui,
“Novel Voltage-Mode Biquad Using Only Active Devic-
x 0
x
S

3
x
S

0ma
g
–0.33 –1.0
1ma
g
0 0
2ma
g
0 0
3ma
g
0.33 0
0mb
g
0.33 1.0
1

0.33 0
2

0.33 0
3

0.33 0

G. N. SHINDE ET AL.
70
es,” International Journal of Electronics, Vol. l87, No. 3,
2000, pp. 307-314.
[12] R. Nandi “Active R Realization of Bilinear RL Imped-
ances and their Applications in a High-Q Parallel Reso-
nator and External Oscillator,” Proceeding of the Institute
of Electrical and Electronics Engineering, Vol. 66, No.
12, 1978, pp. 1666-1668.
[13] G. N. Shinde and D. D. Mulajkar, “Electronically Tuna-
ble Current-Mode Second Order High Pass Filter for
Different Value of Q,”International Journal of Physical
Sciences, Vol. 3, No. 6, 2008, pp. 148-151.
[14] D. R. Bhaskar, U. R. Sharma and S. M. I. Rizvi, “New
Current-Mode Universal Biquadratic Filter,” Microelec-
tronic Journal, Vol. 88, No. 10, 1999, pp. 837-839.
[15] S. Minaei and S. Turkoz, “Current-Mode Electronically
Tunable Universal Filter Using Only Plus-Type Current
Controlled Conveyors and Grounded Capacitors, Band-
pass High Pass Filter,” ETRL Journal, Vol. 26, No. 4,
2004, pp. 292-296.