Hardware Reference
In-Depth Information
Chapter 7
Realization of Sinusoidal Oscillators
Using CCs
Abstract Single capacitance/resistance controlled sinusoidal oscillators using CCs
have been discussed which include both single CC-based as well as two or more
CC-based oscillators including quadrature and multiphase oscillators. Also
included are fully-uncoupled oscillators and oscillators employing all grounded
passive elements as well as those providing explicit current output.
7.1
Introduction
This chapter is concerned with the realization of single-capacitance/resistance
controlled sinusoidal oscillators using CCs a wide variety of which have been
advanced during the last 35 years or so [
1
-
56
].
Because of their numerous applications in electronics, communication, instru-
mentation, measurement and control, sinusoidal oscillators have been a major topic
of research since long. In communication systems, sinusoidal oscillators are used to
generate a carrier signal in modulators, in instrumentation and measurement sys-
tems they may be employed as test oscillators employed in measurement and sensor
applications as well as transducer oscillators in conjunction with resistive/capaci-
tive/ inductive transducers.
With the advent of the integrated circuit (IC) op-amps, it was a logical conse-
quence to have op-amp-based configurations for realizing a number of classical
sinusoidal oscillator topologies such as Wien bridge oscillator, RC-phase shift
oscillator and twin-T oscillators etc. for low to medium frequency applications. A
common difficulty with the mentioned topologies was recognized to be their
inability to provide variable frequency oscillations through only a single variable
element, preferably a variable resistor. Hribsek and Newcomb were the first to
propose a single-resistance-controlled oscillator using two IC op-amps [
62
]. Since
then, efforts of the researchers were soon directed towards devising new topologies
for such single-element-controlled oscillators (SECO)/SRCOs employing a single
op-amp along with a canonical number of passive components namely, only two
capacitors and at most five resistors. A number of such single-op-amp SRCOs have
since been discovered, for instance, see [
63
-
69
] and those cited therein.
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