hello this is an introductory course on circuits
and systems or networks and systems
suitable for an under graduated students major
in electrical engineering with either to power
or communication
option in this course we will study the dynamic
behavior of systems and networks you will
be expose to a
variety of tools and techniques which are
used to study the behavior of the systems
under with the dynamic
inputs so that you can gain an or what particular
techniques to choose under a given situation
when talking about systems we should also
talk about signals the input variables to
a system the response
variable that where looking for and the various
intermediate variables which occur a different
points in
the system are all collectively called signals
and this is the term which we will use to
describe this
variables associated with systems later on
we will say that a network is a special kind
of systems and
the voltage and current variables associate
with a circuit or a network therefore are
also called signals
in the particular contest of a electrical
work these signals are usually functions of
time a study of
the characteristic of the signals and there
analysis therefore it an integral component
of our course
as a matter of fact it is the interplay between
the signals and systems that will be the main
theme or
and focus of our course among the topics which
will study or for your methods for your transform
laplace transform method network functions
and network theorems z transform methods and
state variable
techniques these will be the various topics
that will be broadly covered under this course
we shall
for the most part confine ourselves largely
to the discussion of linear time invariant
systems the
meaning of these 2 adjectives linear and time
invariant will become clear as we go along
suppose is to say that the
form a large class of useful systems so at
the end of this course you will have with
you a tool kit of available
techniques so that you can choose 1of these
took techniques for the solution of with a
dynamic behavior of a
network and system belonging to this very
large class of linear time invariant systems
before a proceed
before we proceed further to discuss the meaning
of a system let me first talk about the various
text books
and reference books that we may like to refer
to during the your study of the material under
this course
you may use this book to have some of your
doubts clarify to deepened your understanding
of a particular
topic may be to get additional information
related to some of the topics that are discussed
here but most
importantly you should this book for working
out the various problems and answering the
various questions
that are given as exercises in this book particularly
for a subject with an analytic analytic orientation
like network and systems it is very important
that you should work out a large number of
this quantitative problems and answer this
various questions
it is only through such exercises that you
can from your understanding with the subject
make your grip
of the various techniques stronger and another
important aspect with this is that like an
any other
discipline in network and systems also there
will be always a number of approaches to solve
a
particular problem only through working out
to this various exercises you will be having
the ability
to choose a the most direct method of attack
for any 1problem you have necessary expertise
to gain the
insight so that you can select the most appropriate
method of attack for the solution of a problem
and
not only that to carry out the solution correctly
and in quick time so i would once again emphasize
the importance of working out a variety of
problems and you can use some of the text
books which
i am going to mention right now ah as a source
material for this problems now the
particular text books that i would like to
recommend are hayt and kemmerly engineering
circuit
and analysis van valkenburg network analysis
these 2are very popular books in this field
openheim willksy and young signals and systems
is a very comprehensive gives a very comprehensive
coverage of the topic that are covered in
this course that’s an additional topics
and this also
contains a wealth of problems and exercises
in addition to these 3 books you
have a book by cheng titled analysis of linear
systems liu and liu linear systems analysis
and
a sixth book by aatre network theory and filter
design it contains discussion of some other
topics we are going to cover in this course
like state variable methods and so on which
are
not perhaps found in some of the other books
by way of a background i expect of you to
follow
this course let me mention that ah i expect
the students to have a background on the following
topics i assumed that you had a basic course
in electrical circuit analysis
which includes the discussion of the properties
of various circuits elements dc and ac circuits
analysis ac circuit analysis on the study
state sinusoidal conditions and an idea of
elementary
transients time constants and rc circuit rl
circuit and so on and setting up the differential
equation pertaining to simple circuits this
is a background in electrical engineering
that 1you
have as per mathematics systems and you should
be familiar with elements of differential
and integral calculus solution of simple linear
differential equations ordinary differential
equations a constant coefficient you should
also have an idea of matrices and determinants
solution of linear algebraic equations and
then elements of complex variable theory is
also
expected a few to follow this course so this
is the background what 1would expect you to
have
follow this course now let us discuss what
a system means all of us have an idea what
a
system is constituted of through its usage
in every day terminology we may formally say
a system
is a collection of components put together
to serve a particular purpose these components
are
are system components that are unified through
some kind of int inter dependence among
them they react with each other so that the
whole system function as a whole to serve
a particular
purpose you may think of a power system the
national educational system hospital systems
railway
systems transportation systems and so on and
so forth many of these systems also have as
a integral
component the interaction of people for example
in social economic system all these are constituents
of systems now therefore a system is a collection
of objects united through some form of interdependence
among the various components or sub systems
as you may call now the variables that describe
the status of
this various components and a system may be
quite diverse depending upon the nature of
the component the
nature of the system and so and so forth for
example if you are talking about an electro
mechanical
system you may have the electrical variables
voltage and current associate with a electrical
components
and mechanical variables like force and velocity
which describe the status of the mechanical
components
at the particular point of in the system at
a particular point in the system therefore
system is a_
concept which includes the whole variety of
ah situations that once comes across now what
about a network
literally speaking a network is a structure
which resembles a kind of net but in our particular
contest
the term network to describe a system in which
all the components are of a related kind that
means the
variables which are of importance in this
system are all of the same kind so in a particular
electrical
network for example is a special kind of a
system in which the variables are voltages
and currents most
often that is these are the 2variables which
are the interest towards the electrical network
similarly
we can have a network representing a mechanical
system which will call a mechanical network
we use the
variables may be velocities and then force
and so on and so forth so we can think of
a net network as a
special kind of a system in electrical network
in particular is what constitutes the focus
of our
discussion here now we analyzing these systems
and networks the first up usually is to model
the system
in terms of idealized components put together
in a particular fashion this evolution of
the model is
d1with 2conflicting requirements in our mind
what are the 2conflicting requirements first
of all we
should like to have the model as realistic
as possible so that it stimulates the real
system in other
words we should like to make the model as
complex as possible so that we loose as little
information
about the system as possible on the other
hand we should also like to make the model
as simple as possible
to lend itself to convenient mathematical
analysis so that the person uses this model
for analysis and
synthesis we retain a sanity in a sense because
if it is going to be a huge a complex type
of model
we will be never to able solve it therefore
these are the 2conflicting requirements in
the evolution of
a model of a given physical system the on
1hand it should be as complex as possible
so that it will
loose as little information about the system
as possible at the same time it has got to
be simple enough
to be lend itself to convenient mathematical
analysis now we are very often refer to the
model itself
as a system even though we must always keep
at the back of our mind that the model is
a mathematical
representation is an idealized representation
the physi the actual physical system is something
different
and some in some ways a physical system may
not the characteristic may not agree with
a model and if it
so then we have to the find the model to make
it more realistic where ever it is warranted
now in arri
in arriving at a model for a particular system
the derivation of the model is specific to
the particular
discipline you must study the situation you
must know the characteristic of these and
arrive a
suitable model but once we have evolved a
model then a whole lot of the system can be
analyses through
a common frame work a common set of mathematical
tools which can be used to analyze a whole
lot of this
different system system models because the
mathematical equations that govern the operation
of the various
system are more or less the same therefore
there is a unifying body of techniques and
knowledge which
come under the general title system theory
at principle of the system analysis which
will be the main scope
of our study in under this course
