Hardware Reference
In-Depth Information
I
HP
I
in
¼
s
2
C
1
C
2
R
3
R
2
R
1
Ds
ð
12
:
124
Þ
ðÞ
Further, if
I
i
2
¼
I
in
, an inverting APF is easily obtainable from
I
01
as
given by the following CM transfer function:
0 and
I
i
1
¼
I
i
3
¼
s
2
C
1
C
2
R
3
R
2
R
1
I
AP
I
in
¼
I
01
I
in
¼
sC
2
R
2
R
3
þ
R
1
ð
12
:
125
Þ
Ds
ðÞ
Case-II
BPF: if
I
i
1
¼
I
i
2
¼
0 (open circuited),
I
in
¼
I
i
3
and
I
out
¼
I
01
; LPF: if
I
i
1
¼
I
i
3
¼
0
(open circuited),
I
in
¼
I
i
2
and
I
out
¼
I
01
; Notch: if
I
i
2
¼
I
i
3
¼
0 (open circuited),
I
in
¼
I
i
1
and
I
out
¼
I
01
; LPF: if
I
i
2
¼
I
i
3
¼
0 (open circuited),
I
in
¼
I
i
1
and
I
out
¼
I
03
;
APF: if
I
i
2
¼
0 (open circuited),
I
in
¼
I
i
1
¼
I
i
3
and
I
out
¼
I
01
; HPF: if
I
i
2
¼
I
i
3
¼
0
(open circuited),
I
in
¼
I
i
1
and
I
out
¼
(
I
03
+
I
01
).
The filter parameters
ˉ
0
and Q
0
are given by:
r
1
C
1
C
2
R
3
R
2
r
C
1
C
2
R
2
R
3
ω
0
¼
andQ
0
¼
R
1
ð
12
:
126
Þ
Thus, from the equation (
12.126
) it is clear that
ˉ
0
and Q
0
can be controlled
orthogonally.
It is, thus, seen that the circuit has the flexibility to be used as either a single-
input three-outputs or three-input two-outputs. Single-input three-output operation
yields LPF, BPF and notch responses simultaneously while HPF can also be
realized by adding appropriate output currents. Three-input two-output operation
offers the realization of all five generic filter functions by proper selection of input
currents. The filter parameters
ˉ
0
and Q
0
can be controlled orthogonally.
From the SPICE simulations, the proposed analog filter was found to be oper-
ating satisfactorily while operating at 3.183 MHz and with power dissipations of the
order of 0.433 mW and the chip area of the filter was 0.022 mm
2
. The functionality
of the design was also verified [
98
] by the post-layout simulations.
Ibrahim
'
s SIMO-type CM biquad An electronically-tunable SIMO-type CM
biquad filter configuration suitable for easy cascading employing two DO-ICCIIs,
one triple output ICCII (TO-ICCII), two grounded capacitors and two MOSFETs as
resistors was proposed by Ibrahim in [
99
]. The presented circuit configuration can
realize LPF, BPF and HPF responses simultaneously from the high output imped-
ance nodes without any component matching condition. The other two responses
namely, notch and APF can also be obtained by connecting appropriate output
currents. The filter parameters
ˉ
0
and Q
0
can be controlled electronically through
the bias voltages of the MOSFETs. Assuming triode region operation of the
MOSFETs, their resistance values is given by:
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