Download independent current sources

REPORT ON INDEPENDENT AND
DEPENDENT SOURCES
GROUP NO: - G-1
CLASS: F.E-SEC: B (CIS)
ROLL NOS: - CS-77
CS-112
CS-115
ACTIVE ELEMENTS:
They are capable of generating energy.
E.g.:- 1) voltage source
2) Current source
PASSIVE ELEMENTS:
They are incapable of generating of energy
e.g. 1) resistors
2) Capacitors
3) Inductors
Voltage sources and the current sources, being active elements delivers power to the elements
connected to them.
There are two types of sources:

independent sources

dependent sources
INDEPENDENT SOURCES:It may be defined as,
“Independent sources are unaffected by the other elements present in the circuits i.e. they do not
controlled by other’s generated voltage or current.”
EXPLANATION:
The behavior of independent sources can be explained by the fact that the voltage drop across the
terminals is independent of the load connected to it. The power requirement of the load is determined
by the amount of current which is being providing at the defined value of the voltage.
Similarly, for the current source, the power requirement is determined by the amount of voltage
providing at the specified current source.
Thus, we can say that these linear elements are independent of the other elements present in the
circuit.
TYPES OF INDEPENDENT SOURCES:
There are two types of independent sources:


independent voltage source
independent current source
INDEPENDENT VOLTAGE SOURCES:Independent voltage sources maintain a voltage across its terminals. It is independent of the other
elements and the current flowing across it.
Output voltage does not depend upon the voltage or current in the other part of the network.
CIRCUIT REPRESENTATION:-
Figure 1
As shown in fig 1, the polarity is enclosed in a circle representing defined voltage.
INDEPENDENT CURRENT SOURCES:An independent current source maintains current across its terminals. It is independent of the other
elements.
Output current does not depend upon the voltage or current in the other part of the network.
CIRCUIT REPRESENTATION:Figure 2
As
figure
are
in a
shown in
2.
The
arrows
enclosed
circle
representing current
EXAMPLES OF INDEPENDENT SOURCES:One of the most common physical examples of independent source is battery which is an
electrochemical device convert’s stored chemical energy into electrical energy. Batteries are commonly
used as energy sources in many household and industrial applications.
Figure 3
DEPENDENT SOURCES:Now talking about dependent sources,
“Such sources that depends on the other element’s generated voltage or current”
Or
“Output voltage or current depends upon the voltage or current in any other part in the network”
Dependent sources only produce a voltage or current when an independent voltage or current source is
in the circuit.
EXPLANATION:The behavior of dependent sources can be illustrated by the fact that the sources, voltage or current,
can be altered by the changing conditions of the circuits since the output result depends on the input
values.
For dependent sources, it is essential to use diamond shaped figure in order to make a difference
between dependent and independent sources
They may be classified as:
 voltage source
 current source
But before discussing these, we will discuss about the factor that is being multiplied by the current or
voltage values of a source, known as “GAIN PARAMTERS”

GAIN PARAMETERS:-
“It is the ratio of output power to the input power”
But in case of voltage and current it is unclear but still we use it to define the factor multiplying by the
values.
Now, we will discuss the types of dependent sources separately.
 VOLTAGE SOURCE:It maintains the voltage across its terminals.
Two types of voltage sources are there: voltage control voltage source
 current control voltage source
 VOLTAGE CONTROL VOLTAGE SOURCE:It is defined as,
”the voltage equal to constant times the voltage generated by a source”
The
voltage
terminals
the voltage or
appearing
the circuit.
across
the
depends upon
current that is
elsewhere in
Figure 4
Here, the voltage of the dependent source will be V=a Vx, where a is the gain parameter and it has no
unit (V/V).because voltage is “a” times the value of voltage.
EXAMPLE:OPERATIONAL AMPLIFIER is the common example
of voltage control voltage source .Since the output
voltage is directly proportional the input voltage.
It is the device used to perform mathematical
operations like multiplication, division, subtraction,
differential, integration etc.
 CURRENT CONTROL VOLTAGE SOURCE:It is defined as,
“The voltage equal to the constant times the current generated in the circuit”
Figure 5
Here, in the above circuit. The value of dependent current source will be V=d ix
Where “d” is the gain parameter whose unit is (V/A)
EXAMPLE:Electric generators are the example of current control voltage source in which the voltage induces in
one winding depends on the current in a second winding.
It is a device used to convert mechanical energy into electrical energy.
Figure 6
 CURRENT SOURCES:Current source delivers a current which is proportional to the current or voltage elsewhere in the circuit.
They may be classified as:


Voltage control current source
Current control current source
 VOLTAGE CONTROL CURRENT SOURCE:It is defined as,
“The current is equal to the constant times the voltage generated in the circuit”
CIRCUIT REPRESENTATION:-
Figure 7
Here, again the value
will be I=b Vx
of dependent source
Where “b” is the gain parameter which has a unit (A/V)
EXAMPLE:
Operational Tran’s conductance amplifier is an example of voltage control current source.it is an
amplifier whose input voltage produced an input current.
Figure 7
 CURRENT CONTROL CURRENT SOURCE:It is defined as,
“The current is equal to the constant times the current generated by a source”
CIRCUIT REPRESENTATION:-
Figure 8
Here, the gain parameter which has a value “c” has no unit since (A/A)
EXAMPLE:TRANSISTORS are the example of current control current source where output current is proportional to
the input current.
Figure 9
COMPARISON BETWEEN INDEPENDENT AND DEPENDENT SOURCES IN
CIRCUIT ANALYSIS:


When performing nodal and mesh analysis we treat dependent sources same as we treat
independent sources in circuit analysis.
In case of super position theorem, we do not treat dependent source as we treat independent
sources. Here dependent sources remain on.
Kirchhoff’s current and voltage laws are applicable for dependent sources.
-maintains the prescribed current voltage
across its terminals regardless of the current
or voltage drawn from it.
•
•
A voltage or current source whose value
“depends” on the value of voltage or current
elsewhere in the circuit
Use a diamond-shaped symbol
LOADCurrent
+
0.012
A
Vs
12 V
Z=A+jB
DC 1e-009Ohm
LOAD
. The usual symbols are shown in figure.
Two particular examples are short-circuiting an
independent voltage source and open-circuiting an
independent current source. Both are not permitted.
An independent source outputs a fixed voltage
or current, independent of any other circuit
parameter. An idealized battery is an example.
Dependent sources have an output they depends upon
an isolated control input. You can have voltagecontrolled-voltage sources, current-controlled voltage
sources, voltage-controlled-current sources, etc. They
are idealized devices.
REFERNCES:







"Amplifier for Electric Currents". United States Patent and Trademark Office.
"Device for Controlling Electric Current". United States Patent and Trademark Office.
"Twists and Turns in the Development of the Transistor". Institute of Electrical and
Electronics Engineers, Inc...
“Electrical engineering, principles and applications”, third edition by ALLAN R HAMBLEY.
http://en.wikipedia.org/wiki/Power_gain.
http://circuits.solved-problems.com/413/ideal-independent-sources/.
“Fundamentals of electric circuits”, third edition by ALEXANDER SADIKU.
“Basic electrical engineering”, fifth edition by A.E. FITZGERALD, DAVID E.
HIGGINBOTHAM, ARVIN GRABEL.