Hardware Reference
In-Depth Information
6.2.3.5 Single-Input-Multi-Output (SIMO)-Type CM Biquads
In the following sub-section, we present a selected number of current-mode biquads
chosen from a large number of available ones [
22
-
27
,
70
,
71
,
75
,
76
,
80
,
87
,
97
,
101
,
104
,
106
,
115
,
118
,
136
,
140
,
141
,
143
,
146
,
147
,
148
,
162
].
Ozoguz and Acar CM Universal Biquad The circuit shown in Fig.
6.26
was
proposed by Ozoguz and Acar [
22
] and is based on an approach involving RLC
shunt circuit (presented in [
24
] and to be spelt out explicitly later in this subsection)
which realizes inverting type LPF, HPF and BPF simultaneously employing a
minimum number of passive components and without requiring any component
matching conditions. Although this filter circuit does not offer independent control
of Q
0
and
ω
0
, nevertheless, Q
0
can be made controllable by connecting a grounded
resistor in parallel with the input signal I
in.
The various transfer functions realized by this configuration are given by:
C
1
R
1
1
s
s
2
I
01
I
in
¼
I
02
I
in
¼
C
1
R
1
C
1
R
1
;
1
1
C
1
C
2
R
1
R
2
1
1
C
1
C
2
R
1
R
2
s
2
þ
s
þ
s
2
þ
s
þ
1
C
1
R
1
C
1
R
2
I
03
I
in
¼
C
1
R
1
C
1
C
2
R
1
R
2
:
ð
6
:
40
Þ
1
1
s
2
þ
s
þ
The notch filter can be obtained by adding I
01
and I
03
while by replacing CCII
2
+by
CCII
2
and then adding I
01
,I
02
and I
03
, an APF can also be realized.
Abuelma
'
atti and Shabra CM Universal Biquad: A novel CC-based universal
CM filter with one input and four outputs employing all grounded passive compo-
nents, presented by Abuelma
atti and Shabra [
23
], is shown in Fig.
6.27
.
'
The proposed configuration can yield all type of responses simultaneously. In all
the filter responses,
ω
0
can be controlled by a grounded resistor without disturbing
ω
0
Q
0
which can also be tuned by another resistor without disturbing
ω
0
. The circuit,
when implemented with AD844s has shown results which are in good conformity
with the theoretical analysis.
A simple approach of deriving SIMO-type CM biquad filters A simple
approach of deriving SIMO-type CM biquad filters was presented by Senani in
[
24
]. The basic idea of this methodology is the simple (but not so obviously
recognized before its disclosure in [
24
]) observation that the currents through the
inductor, resistor and the capacitor represent respectively a second-order LPF, BPF
and HPF responses and hence, if these currents can be sensed out by using either
CCII
or CCI- as shown in Fig.
6.28
.
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