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y
x
CCII+
z
R
6
I
in1
C
1
C
3
x
y
x
I
in3
CCII+
z
y
z
y
CCII+
z
CCII+
x
R
5
R
2
R
4
x
y
x
CCII-
z
CCII-
R
8
R
7
z
y
I
in2
I
0
Fig. 6.36 MISO-type universal CM biquad using CCII+ s proposed by Abuelma
atti and
'
Tasadduq (Adapted from [
31
]
1997 Elsevier)
©
I
3
¼
I
2
¼
0, I
1
¼
I
in
; BPF: I
1
¼
I
3
¼
0, I
2
¼
I
in
; HPF: I
1
¼
I
2
¼
0 and I
3
¼
I
in
; Notch:
I
2
¼
R
7
.
This circuit was experimentally tested using AD844 as CCII+. The results
obtained had excellent agreement with theoretical results.
0, I
1
¼
I
3
¼
I
in
and R
5
¼
R
6
; and APF: I
1
¼
I
2
¼
I
3
¼
I
in
, and R
5
¼
R
6
¼
Abuelma
'
atti and Al-Zaher Biquad Another three-input-single-output CM
biquad employing four CCIIs+, five grounded resistors and three grounded capac-
itors, which was proposed by Abuelma
atti and Al-Zaher in [
32
], is shown in
'
Fig.
6.37
.
This filter configuration offers independent control of filter parameters
ω
0
and
Q
0
through grounded resistors and has low active and passive sensitivities.
Assuming ideal CCIIs+ the expression of the output current in terms of the
various input currents is found to be:
ω
0
s
2
C
C
6
I
3
C
6
R
4
I
2
þ
I
1
s
1
1
C
1
C
6
R
2
R
4
R
4
R
7
C
6
R
6
I
0
¼
ð
6
:
57
Þ
1
1
C
1
C
6
R
2
R
5
s
2
þ
s
þ
From Eq. (
6.57
), the following filter responses can be derived: LPF: I
3
¼
I
2
¼
0,
I
1
¼
I
in
; BPF: I
1
¼
I
3
¼
0, I
2
¼
I
in
; HPF: I
1
¼
I
2
¼
0 and I
3
¼
I
in
; Notch: I
2
¼
0,
I
1
¼
I
3
¼
I
in
with R
5
¼
R
6
; and APF: I
1
¼
I
2
¼
I
3
¼
I
in
along with R
5
¼
R
4
and
C
3
¼
C
7
.
The circuit had been practically implementable with AD844 and provides the
following advantages: use of only one type of CCs namely, CCII+, all resistors and
capacitors being grounded, low active and passive sensitivities, independent control
of
ω
0
and band width using grounded resistors and the feasibility of realizing all the
five standard filter functions without any component matching.
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