Hardware Reference
In-Depth Information
Fig. 6.14 VM MISO-type
universal biquadratic filters
proposed by Horng [ 12 ]
R 1
V 2 +
-
C 1
CCII-
x
+
-
V 3
z
y
V 0
C 2
R 2
CCII-
x
z
y
+
-
V 1
Horng ' s Universal Biquad Two MISO-types VM universal biquadratic filters
were introduced by Horng [ 12 ] employing two minus type CCIIs, two capacitors
and two resistors.
Both the topologies are capable of realizing LPF, BPF, HPF and notch functions
whereas the APF could also be obtained by using one more inverting amplifier to
invert one of the voltage signals. One of these circuits is shown in Fig. 6.14 .
Assuming ideal CCIIs, the expression for V 0 for the circuit of Fig. 6.14 is given by
V 3 þ
s 2 C 1 C 2 R 1 R 2
ð
sC 2 R 2
Þ
V 2 þ
V 1
V 0 ¼
ð
6
:
25
Þ
s 2 C 1 C 2 R 1 R 2 þ
sC 2 R 2 þ
1
The various filter responses can be realized as follows: HPF: if V 1 ¼
V 2 ¼
0
(grounded) and V 3 ¼
V in ; BPF: if V 1 ¼
V 3 ¼
0 and V 2 ¼
V in ; LPF: if V 2 ¼
V 3 ¼
0
and V 1 ¼V in ; Notch:
if V 2 ¼0 and V 1 ¼V 3 ¼V in and finally, an APF:
if
V 1 ¼
V in .
This circuit successfully realizes all the five filter responses using AD844 with
the all-pass also realizable by implementing the required inverting amplifier using
an AD844 and two additional resistors.
V 2 ¼
V 3 ¼
Chang and Tu Universal Biquad The circuit of Fig. 6.15 proposed by Chang and
Tu [ 13 ] employs two CCII+ s, two capacitors and three resistors with four inputs
and one output.
The circuit is capable of realizing all standard second-order filter responses
where
ω 0 and Q 0 can be controlled orthogonally. Circuit analysis yields the
expression for the output voltage V out (assuming ideal CCIIs) as:
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