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ICCII
z
31+
y
(3)
x
z
32-
C
2
I
in1
I
out
ICCII
ICCII
I
in4
z
21+
I
in2
z
11+
y
(2)
y
(1)
z
22-
z
12-
x
C
1
x
I
in5
R
2
R
1
I
in3
Fig. 12.29 CM universal filter proposed by Horng [
97
]
f
o
of 1.59 MHz. The SPICE generated frequency responses of LP, BP and HP are
shown in Fig.
12.28b
which confirm the validity of the circuit of Fig.
12.28a
.
Horng
'
s MISO-type CM biquad In 2011 Horng [
97
] proposed a MISO-type CM
universal biquad structure as shown in Fig.
12.29
employing three ICCIIs, two
grounded capacitors and two resistors.
The configuration can yield all five second-order filter responses without any
critical matching of elements. Assuming ideal ICCIIs, a routine circuit analysis
gives the output current in terms of input currents as:
R
1
C
1
I
in
2
I
in
1
þ
s
2
ð
I
in
3
þ
I
in
4
þ
I
in
5
Þ þ
s
1
ð
I
in
5
Þ þ
1
C
1
C
2
R
1
R
2
ð
I
in
4
þ
I
in
5
Þ
R
1
C
1
I
out
¼
1
1
C
1
C
2
R
1
R
2
s
2
þ
s
þ
ð
12
:
118
Þ
From equation (
12.118
), it is seen that the various filter responses can be obtained as
follows from this circuit:
HPF: if
I
in
1
¼
I
in
2
¼
I
in
4
¼
I
in
5
¼
0 (open circuited) and
I
in
¼
I
in
3
;
BPF: if
I
in
1
¼
I
in
3
¼
I
in
4
¼
I
in
5
¼
0 (open circuited) and
I
in
¼
I
in
2
;
LPF: if
I
in
3
¼
I
in
2
¼
I
in
4
¼
I
in
5
¼
0 (open circuited) and
I
in
¼
I
in
1
;
Notch: if
I
in
1
¼
I
in
2
¼
I
in
3
¼
I
in
5
¼
0 (open circuited) and
I
in
¼
I
in
4
; and
APF: if
I
in
1
¼
I
in
5
.
Chen
'
s MIMO-type CM biquad Another MIMO-type CM filter configuration
was proposed by Chen [
98
] using three DO-ICCIIs and five grounded passive
elements. The circuit is shown in Fig.
12.30
.
By straightforward circuit analysis of Fig.
12.30
gives the following CM transfer
functions:
I
in
2
¼
I
in
4
¼
I
in
3
¼
0 (open circuited) and
I
in
¼
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