Hardware Reference
In-Depth Information
Fig. 7.4 The SRCO
proposed by Jana and Nandi
[
6
]
C
x
R
x
x
CCII+
z
y
R
1
R
2
C
1
C
2
offset voltage at terminal-Z. This is an advantage of the suggested modification in
the oscillator of Jana and Nandi [
6
].
After the introduction of the above mentioned circuits by different researchers, a
number of systematic studies were conducted by several authors such as by
Abuelma
atti and Humood in [
8
-
10
] and Celma et al. in [
16
] to derive single-
CC-based cananoic SECOs/SRCOs and it was eventually established that only five
passive components are really necessary alongwith a single CC, to make either a
single-capacitor-controlled oscillator (SCCO) or SRCO; two resistors and three
capacitors for the former and two capacitors and three resistors in case of the latter.
An exemplary SCCO/SRCO (both derivable from each other through RC:CR
transformation) is shown in Fig.
7.5
. It is interesting to note that the SRCO of
Fig.
7.5
was independently proposed by Abuelma
'
atti and Humood in [
10
] as well
'
as by Celma et al. in [
16
].
The CO and FO for this circuit are given by
R
R
2
¼
C
2
C
1
1
þ
ð
7
:
14
Þ
r
2
C
1
C
2
RR
1
and
ω
0
¼
ð
7
:
15
Þ
from where it is readily seen that CO is controllable by R
2
whereas FO is indepen-
dently adjustable by R
1
.
7.3 SRCOs Employing Grounded Capacitors
It is well known that the circuit configurations employing all grounded capacitors are
attractive not only from the view point of IC implementation but also due to the fact
that they can easily accommodate the parasitic capacitances of the active devices
employed which can be absorbed in them. It is worth pointing out that using the
traditional op-amps, a number of circuits are known in literature which employ
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