Arab Academy for Science
, Technology and Maritime
Transport
Analog and Digital Circuits
Analysis
EC 334
Prof. Dr. Mohamed Hassan
important hints
• Any problem just contact Dr.
mhabdazeem@hotmail.com
Room 308 A
• Bonus marks are allowed through good participation in
lectures .
• Lecture Attendance is very important.
• You have to get the lectures with you each time (printed or
on PDAs) to follow up.
• You have to be prepared for tutorials activities each time
(calculator-papers-pen……
Course Assessment
30% 7th week exam
20 % 12th week exam
10% tutorial activitie
(attendance- exams-home works-class
activities)
40% final term exam
Prerequisite:
Textbook:
EC233 and EE232
K.M. Soni, Circuits and systems, Kataria & sons, 2008
Reference book: J. W. Nilsson and S. A. Riedel, “Electric Circuits”,
eghith Edition. Upper Saddle River, NJ: Prentice Hall,
2010.
Course Description and Aim:
Circuit analysis, Laplace transform, two port networks, digital circuits and
logic gates.
To be familiar with circuit synthesis techniques, circuit analysis and logic
gates.
Lecture 1
Contents:
1. Part 1 : Introduction
2. Part 2 : Basic Circuit Elements
Part One
Introduction
The science of electrical engineering is concerned with
the design and the analysis of electrical circuits.
ELECTRICAL CIRCUITS
Lumped Circuits
24 September 2013
Distributed Circuits
Dr. MOHAMED HASSAN
What are the main circuit
elements?
 There are active elements & passive elements
 Active elements can generate energy
 Voltage and current sources
+
V
I
–
 Passive elements cannot generate energy
 Batteries
 Resistors
R
 Capacitors and Inductors (but CAN store energy)
24 September 2013
Dr. MOHAMED HASSAN
What are the main circuit variables?
 Basic variables: current (I) , voltage (V) and power (P)
 Current: time rate of change of electric charge
I = dq/dt
A
1 Amp = 1 Coulomb/sec
 Voltage: electromotive force or potential,
V =dW/dq
1 Volt = 1 Joule/Coulomb = 1 N·m/coulomb
 Power:
P = dW/dt = I V
1 Watt = 1 Volt·Amp = 1 Joule/sec
 Energy:
24 September 2013
W   pdtJouls
Dr. MOHAMED HASSAN
Current, I
 Normally we talk about the movement of
positive charges although we know that, in
general, in metallic conductors current results
from electron motion .
 The sign of the current indicates the direction
I(t)
of flow.
 Types of current:
 direct current (dc): batteries and some
special generators
 alternating current (ac): household current
which varies with time
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Dr. MOHAMED HASSAN
24 September 2013
Dr. MOHAMED HASSAN
Voltage, V
Voltage is the difference in energy level of a unit
charge located at each of two points in a circuit,
and therefore, represents the energy required to
move the unit charge from one point to the other.
Voltage Drop
Circuit Element(s)
+
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V(t)
–
Dr. MOHAMED HASSAN
Power, P
I
+
Circuit Element
–
V
P=IV
 Positive (+) Power: element absorbed
power
 Negative (-) Power: element delivered
power
24 September 2013
Dr. MOHAMED HASSAN
Example
 Calculate the power delivered or absorbed by each element
in the shown circuit. Show that the sum of the delivered
power = sum of the absorbed power (balanced circuit)
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Dr. MOHAMED HASSAN
Solution
P (delivered) = (-1000) + (-20) + (-140) = -1160
W
P 2013
(absorbed) = 200
+ 600 +
360 = 1160 W
24 September
Dr. MOHAMED
HASSAN
P (delivered) + P (absorbed) = 0
Part 2
Basic Circuit Elements
Active Elements
Passive Elements
Sources
R, L, C
Dependent
Independent
Voltage
Current
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VCVS
CCVS
Dr. MOHAMED HASSAN
VCCS
CCCS
2.1 Ideal Independent
Sources
v&i
Ideal sources maintain either constant
voltage or constant current.
vs
Ideal
+
-
v source
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 Ideal sources don’t really
exist
 You can’t compute
v across i source or i across v
source (no i = f(v) or v=g(i))
 Are not dependent on
anything else
is
Ideal
i source
Dr. MOHAMED HASSAN
2.2 Ideal Dependent
Sources
v&I
Ideal sources controlled by other circuit
elements
vs =
mvx
or
ri x
Ideal
+
-
v source
24 September 2013
 they are controlled from
other places in the circuit
– i.e. controlled sources
 The variants are:
is =
avx
or
bi x
Ideal
 voltage controlled current
source or voltage source
 current controlled current
source or voltage source
i source
Dr. MOHAMED HASSAN
Passive Element:- which can not contribute (add) energy to the-circuit.
Active Element:- Is capable of generating energy (delivers energy to
the circuit).
Sources:- are the circuit elements that are capable of converting nonelectric energy to electric energy.
Indepen. Source:- is an active element that provides a specified
voltage or current that is completely independent of other circuit
variables.
Depend. Source:- is an active element in which the source
quantity is controlled by another voltage or current in the circuit.
►VCVS
Voltage Controlled Voltage Source
►CCVS
Current Controlled Voltage Source
►VCCS
Voltage Controlled Current Source
►CCCS
Current Controlled Current Source
Voltage Source:- Is the circuit element that maintains a prescribed
voltage across its terminals regardless the current flowing in those
terminals.
Current Source:- Maintains a prescribed current through its terminals
regardless
the voltage across
those terminals.
24 September 2013
Dr. MOHAMED HASSAN
2.3 Connecting sources
 Never connect 2 outputs!
 NO voltage sources in parallel
+
vs1
vs1
-
+
-
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+
vs2
vs2
 if vs1 ≠ vs2 =>
 if vs1 = vs2 =>
-
+
smoke
theoretically
possible, but
bad idea
 No problem
 total voltage = vs1 + vs2
-
Dr. MOHAMED HASSAN
2.3 Connecting sources
 Never connect 2 outputs!
 NO current sources in series
is1
is1
24 September 2013
is2
is2
 if is1 ≠ is2 =>
 if is1 = is2 =>
smoke
theoretically
possible, but
bad idea
 No problem
 total current = is1 + is2
Dr. MOHAMED HASSAN
2.3 Connect sources
 Respect current and voltage sources
vs
 DO NOT short circuit a
voltage source
+
-
is2
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 DO NOT open circuit a
current source
Dr. MOHAMED HASSAN
Example :- Using the definitions of the ideal indep. & depen. Voltage &
current sources, state which interconnections are valid and which are
not.
3A
10
V
7A
5V +-
+
-
Vx=5
+
3Vx -
(d)
10
V
(b)
(a)
+
-V
5A
Vx=5
+
-V
4Vx
(e)
+
-
(c)
ix=2A
4ix +-
(f)
Solution
(a) Invalid (b) Invalid (c) Valid
(d) Invalid (e) Valid
(f) Valid
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Dr. MOHAMED HASSAN
ix=2A
5ix
(g)
(g) Invalid
Electric Circuit Topology
Nod
e
Mes
h
Loo
Branc
Node:- A point where two or more
p circuit elements
h meet (1,2,3,4, and 5).
Path:- A trace of adjoining basic elements with no elements included more than
once.
Branch:- A path connecting two nodes (1-2, 2-3, 3-4, 3-5, 1-4,………).
Loop:- A path whose the last node is the same as the starting node (closed
path).
Mesh:- A loop that does not contain (enclose) any other loops (A,B,C, D).
24 September 2013
Dr. MOHAMED HASSAN