Hardware Reference
In-Depth Information
Fig. 6.25 Three-input-two-
output VM universal filter
proposed by Horng [
21
]
CCII+
V
2
y
V
01
z
x
Y
3
Y
4
Y
1
CCII+
x
V
02
z
V
1
y
Y
2
CCII+
y
V
3
x
z
Y
5
The expressions for the output voltages are given by:
Y
2
Y
4
V
1
þ
Y
1
Y
2
V
2
þ
Y
1
Y
5
V
3
V
01
¼
ð
6
:
38
Þ
Y
2
Y
4
þ
Y
2
Y
3
þ
Y
1
Y
3
Y
3
Y
4
V
1
þ
Y
1
Y
3
V
2
Y
5
Y
3
þ
ð
Y
4
Þ
V
3
V
02
¼
ð
6
:
39
Þ
Y
2
Y
4
þ
Y
2
Y
3
þ
Y
1
Y
3
Two choices of the circuit admittances leading to two different biquad filters as
special cases have been elaborated. However, one of these requires three capacitors
leading to a non-canonic structure and is hence omitted. Likewise, the second
configuration proposed in [
21
] has three capacitors in both the choices of compo-
nents therein; hence, this particular configuration is also omitted.
In the configuration shown in Fig.
6.25
only the following choice of components
leads to a canonic structure: Y
1
¼
1/
R
5
. Under these conditions from Eqs. (
6.38
) and (
6.39
), the various filter responses
can be obtained as follows:
(i) For V
2
¼
1/R
1
,Y
2
¼
sC
2
,Y
3
¼
1/R
3
,Y
4
¼
sC
4
and Y
5
¼
V
3
¼
0 (grounded) and V
1
¼
V
in
, HPF can be realized at V
01
and
BPF at V
02
(ii) for V
1
¼
V
3
¼
0 (grounded) and V
2
¼
V
in
, BPF can be realized at V
01
and LPF at V
02
(iii) for V
1
¼
V
2
¼
0 (grounded) and V
3
¼
V
in
, a LPF can be realized
at V
01
(iv) for V
2
¼
0 (grounded), R
3
¼
R
5
and V
1
¼
V
3
¼
V
in
a notch can be
obtained at V
01
(v) for V
1
¼
V
2
¼
V
3
¼
Vin, R
1
¼
R
3
¼
R
5
, an APF can be
realized.
The workability of this circuit has been confirmed with circuits implemented
from AD844 ICs. It was observed that input levels of with 17.3 V p-p are possible
without significant distortion when the AD844 were biased from
10 V Dc power
supplies.
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