Hardware Reference
In-Depth Information
Fig. 12.44 Universal
biquad filter configuration
proposed by Chen [ 205 ]
R 3
R 2
x+
y 1
y 2
z +
V 0
C 2
BDI-
+
z - x-
V 2
-
+
R 1
V 3
+
-
C 1
V 1
-
12.2.11 Filter Design Using Balanced-dual-input Dual-
output-CC (BDI-DOCC)
In this section, we present an interesting biquad filter configuration using yet
another variety of CCs called balanced dual input-dual output CC (BDI-DOCC)
which is shown here in Fig. 12.44 .
A BDI-DOCC is characterized by the following terminal equations:
V X þ ¼
V Y 1 , V X ¼
V Y 2 , I Z þ ¼
I X þ and I Z ¼
I X
ð
12
:
155
Þ
Chen biquad using BDI-DOCC The VM MISO-type filter configuration shown
in Fig. 12.44 employs one BDI-DOCC, two capacitors and three resistors. This
circuit which was proposed by Chen in [ 205 ] offers (i) realization of all standard
second-order filters from the same topology (ii) no requirement of matching
condition(s) of components
(iii)
low active and passive sensitivities and
(iv) orthogonal control of
ω 0 and Q 0 .
Assuming ideal BDI-DOCC, a routine circuit analysis yields the following VM
transfer function:
V 2 þ
V 3
s 2 V 1 þ
s
C 1
1
1
R 3
1
C 1 C 2 R 1 R 2
R 2 þ
V 0 ¼
ð
:
Þ
12
156
s
C 1
1
1
R 3
1
C 1 C 2 R 2 R 1
s 2
þ
R 2 þ
þ
Using the equation ( 12.156 ) all standard second-order filter responses can be found
as follows:
HPF: if V 2 ¼
V 3 ¼
0 (grounded) and V 1 ¼
V in (input signal); BPF: if V 1 ¼
V 3 ¼
0
and V 2 ¼
V in ; LPF: if V 1 ¼
V 2 ¼
0 and V 3 ¼
V in ; Notch: if V 2 ¼
0 and V 1 ¼
V 3 ¼
V in
and APF: if V 1 ¼
V 2 ¼
V 3 ¼
V in .
 
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