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a
b
R
b
R
b
V
in
V
in
y
y
CCII−
z
CCII−
z
x
x
C
R
V
0
V
0
R
C
R
a
R
a
Fig. 6.1 First order voltage-mode all pass filters proposed by Higashimura and Fukui [
1
]
a
b
R
a
R
a
R
C
I
0
x
I
0
x
CCII−
z
CCII−
z
y
y
R
C
I
in
I
in
R
b
R
b
Fig. 6.2 First order current-mode all pass filters proposed by Higashimura and Fukui [
2
]
I
out
I
in
¼
1
sCR
i
out
¼
ð
6
:
2
Þ
1
þ
sCR
where the + sign is applicable to the circuit of Fig.
6.2a
and the - sign is applicable
to the circuit of Fig.
6.2b
. The SPICE simulation results of the circuit of Fig.
6.2b
using a CCII
, based upon
power supply current sensing technique
employing
LF356 type op-amps together with the current mirrors made from pnp transistors
2SC733 and npn transistors 2SC945, have shown that these circuits perform as
predicted by the theory.
Cicekoglu et al. in [
3
] have conducted a systematic generation of CCII+ based
first order all pass sections and derived a set of 22 circuits employing single
capacitor and 2-3 resistors. Out of these 22 circuits, as many as 16 employ a
floating capacitor while the remaining 6 employ a grounded capacitor. In view of
the importance of grounded-capacitor structures, as preferred from IC implemen-
tation view point, these 6 circuits are shown here in Fig.
6.3
.
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