Hardware Reference
In-Depth Information
CCII+
y
x
z
3
R
3
CCII+
y
x
z
2
R
2
CCII+
C
1
CCII+
C
2
CCII+
V
in
y
x
y
x
z
1
y
x
z
6
z
1
V
0
7
R
1
R
/
R
4
R
5
R
/
CCII-
CCII-
x
y
x
y
/
z
4
z
R
1
5
Fig. 6.7 Universal active filter proposed by Toumazou and Lidgey [
7
]
and is shown in Fig.
6.7
. Using ideal port relations of the CCIIs, the transfer
function realized by this configuration is given by
s
2
C
1
C
2
R
4
R
5
=
V
0
V
in
¼
R
3
þ
sC
1
R
4
=
R
2
þ
1
=
R
1
ð
6
:
12
Þ
R
0
3
þ
R
0
2
þ
R
0
1
s
2
C
1
C
2
R
4
R
5
=
sC
1
R
4
=
1
=
from where the various filter responses can be derived as follows: HPF by making
R
1
¼
R
2
¼
1
; LPF by making
R
3
¼
R
2
¼
1
; BPF by making
R
1
¼
R
3
¼
1
; Notch
R
3
,
R
0
1
¼
R
0
2
¼
R
0
3
by making
R
2
¼
1
,
R
3
¼
R
1
and finally, APF by making
R
1
¼
R
2
¼
with CCII2 taken as CCII
.
Using high performance CCII+ and CCII
implemented from Wilsons
'
741-type op-amps and CA3096E mixed transistor arrays, the circuit was found to
give extremely good performance with band pass Q
0
of the order of 200 with very
close performance between experimental and theoretical results.
Another high input impedance universal active filter proposed by Higashimura
[
8
] is shown in Fig.
6.8
. This circuit uses only plus type CCIIs and grounded
capacitors and can yield all the five types of standard filters under appropriate
conditions.
In this circuit, the filter parameters namely,
ω
0
,
Q
0
and voltage gain H
0
can be
controlled by separate resistors. The transfer function of this circuit can be
expressed as:
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