Hardware Reference
In-Depth Information
Fig. 12.10 DVCC-based
tunable CM universal filter
proposed by Chen (Adapted
from [
13
]
©
2011 Elsevier
GmbH)
z+
z+
z+
y
21
3
21
22
23
DVCC
DVCC
V
1
y
22
x
2
z+
y
11
I
01
11
1
C
1
I
i1
R
2
z
12
y
12
x
1
I
03
I
i3
V
2
R
1
C
2
V
3
y
31
z+
DVCC
31
I
i4
z+
y
32
x
3
32
I
02
I
i2
R
3
From the above equation (
12.34
), the various filter responses can be obtained as:
LPF: V
in2
¼
V
in
;
Notch: V
in1
¼
V
in2
¼
0, and V
in3
¼
V
in
; HPF: V
in2
¼
0 and V
in1
¼
V
in3
¼
V
in
; and
APF: V
in1
¼
V
in3
¼
0, and V
in1
¼
V
in
; BPF: V
in1
¼
V
in3
¼
0, and V
in2
¼
R
4.
Thus, all second-order standard filter responses can be realized. The filter
parameters namely Q
0
and
0 and V
in3
¼
V
in2
¼
V
in
, and R
3
¼
ˉ
0
are given by:
r
C
2
R
2
C
1
R
1
r
1
C
1
C
2
R
1
R
2
R
3
R
4
Q
0
¼
and
ω
0
¼
ð
12
:
35
Þ
From equation (
12.35
), it is clear that Q
0
can be varied by R
3
or R
4
and
ˉ
0
can
independently be tuned by R
1
or R
2
provided they are varied simultaneously
thereby keeping Q
0
unchanged.
Chen biquad Figure
12.10
shows a CM MIMO-type versatile tunable DVCC-
based universal filter proposed by Chen [
13
]. The filter circuit employs three plus-
type DVCCs and five grounded passive elements. The structure can be used as either
a single-input and three-output or four-input and two-output circuit. As a single-
input, three-output, the configuration can realize BPF, HPF and notch responses
simultaneously while as a four-input, two-output circuit, the circuit can yield both
inverting and non-inverting LPF, BPF, HPF, notch and APF filter functions simul-
taneously without any component matching condition. The proposed structure offers
orthogonal controllability of
ˉ
0
and Q
0
through grounded passive elements.
By straight forward circuit analysis of Fig.
12.10
, the following CM transfer
functions can be realized:
sC
2
R
3
I
i
4
s
2
C
1
C
2
R
1
R
2
I
i
1
þ
I
01
¼
sC
2
R
3
I
i
2
I
i
3
ð
:
Þ
12
36
s
2
C
1
C
2
R
1
R
2
þ
sC
2
R
3
þ
1
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