Hardware Reference
In-Depth Information
For the circuit of Fig.
11.1a
, the I
0
is given by:
I
A
I
C
2
I
B
I
o
¼
ð
11
1
Þ
:
Hence, the circuit would function as a current-mode multiplier/divider.
For the sinusoidal oscillator circuit of Fig.
11.1b
, the CO and FO are given by:
r
1
C
1
C
2
R
x
1
R
x
2
C
1
¼
C
2
;
ω
0
¼
ð
11
2
Þ
:
Hence, an electronically controllable oscillator is realized. If the DC bias currents
of the two CC-CFAs are taken equal i.e. I
B1
¼
I
B
, it can be easily verified that
ω
0
will become directly proportional to I
B
and the circuit, thus, becomes a
linear
current-controlled oscillator.
In case of the grounded inductance circuit of Fig.
11.1c
, the value of the
simulated inductance is given by:
I
B2
¼
CV
T
4
I
B
1
I
B
2
L
¼
CR
x
1
R
X
2
¼
ð
Þ
11
:
3
For the circuit of Fig.
11.1d
, the output voltage is given by:
V
in
1
s
2
C
1
C
2
R
x
1
R
x
2
þ
V
in
2
1
ð
þ
sC
2
R
x
2
Þ
V
in
3
sC
2
R
x
1
V
o
¼
ð
11
4
Þ
:
s
2
C
1
C
2
R
x
1
R
x
2
þ
sC
2
R
x
2
þ
1
while in case of the circuit of Fig.
11.1e
, the output current is given by:
I
in
3
s
2
C
1
C
2
R
x
1
R
x
2
þ
I
in
1
sC
2
R
x
2
þ
I
in
2
ð
sC
2
R
x
2
þ
1
Þ
I
o
¼
ð
Þ
11
:
5
s
2
C
1
C
2
R
x
1
R
x
2
þ
sC
2
R
x
2
þ
1
From the Eqs. (
11.4
) and (
11.5
) it is easy to figure out that by choosing inputs
appropriately all the five standard filter functions can be realized in both multi-
input-single-output-type VM and CM filters of Fig.
11.1d
and
e
respectively.
11.3 Four-Terminal-Floating-Nullor (FTFN)
The four-terminal-floating-nullor (FTFN) is a conceptual generalization of the
nullor with all the four terminals being floating with the ground terminal being
taken as external, as shown in Fig.
11.2
. In concept, it is similar to an
operational
floating amplifier
introduced by Huijsing [
4
,
5
].
In the literature several
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