basic theory of circuits
DESCRIPTION
Basic Theory of Circuits. SEIEE Shanghai Jiao Tong University 2009.9. Introduction. Course Title: Basic Theory of Circuits Periods/ Credits: 72/4 Prerequisites: Advanced math; General physics Lecturer: Associate Professor Li Ping Email address: [email protected] - PowerPoint PPT PresentationTRANSCRIPT
Basic Theory of Circuits, SJTUBasic Theory of Circuits, SJTU 11
Basic Theory of CircuitsBasic Theory of Circuits
SEIEE SEIEE
Shanghai Jiao Tong UniversityShanghai Jiao Tong University
2009.92009.9
Basic Theory of Circuits, SJTUBasic Theory of Circuits, SJTU22
IntroductionIntroductionCourse Title: Basic Theory of Circuits
Periods/ Credits: 72/4
Prerequisites: Advanced math; General physics
Lecturer: Associate Professor Li Ping
Email address: [email protected]
Lecture time and classroom: 东下院 205 Wed34;Fri12
Tutorial arrangement:
Website: http://ee.sjtu.edu.cn/po/Class-web/dianlu-jichu/index.htm
http://eelab.sjtu.edu.cn/dl/
Assessment:
Basic Theory of Circuits, SJTUBasic Theory of Circuits, SJTU33
Course objective:
The aim and task for this course is to help the students to grasp the circuits concepts correctly, grasp the basic rules and analyzing methods, which provides a solid basis for further study
Basic Theory of Circuits, SJTUBasic Theory of Circuits, SJTU44
Topics covered:Topics covered:
Basic conceptsBasic concepts Lumped-parameter circuitsLumped-parameter circuits VariablesVariables Circuit elements Circuit elements Circuit modelCircuit model Basic rulesBasic rules
Basic Theory of Circuits, SJTUBasic Theory of Circuits, SJTU55
Topics covered:Topics covered:
Analysis of linear resistive networkAnalysis of linear resistive network Mesh analysisMesh analysis Nodal analysisNodal analysis Loop analysis Loop analysis Cut sets analysisCut sets analysis Analysis theoremsAnalysis theorems
Basic Theory of Circuits, SJTUBasic Theory of Circuits, SJTU66
Topics covered:Topics covered:
Analysis of linear dynamic circuitAnalysis of linear dynamic circuit
first-order RC, RL circuitfirst-order RC, RL circuit
Step response and impulse responseStep response and impulse response
second-order RLC circuitsecond-order RLC circuit
Analysis method in frequency domainAnalysis method in frequency domain
Basic Theory of Circuits, SJTUBasic Theory of Circuits, SJTU77
Topics covered:Topics covered:
Analysis of sinusoidal stable stateAnalysis of sinusoidal stable state sinusoidal variable and phastorsinusoidal variable and phastor sinusoidal stable state responsesinusoidal stable state response Circuit analysis in phasor modelCircuit analysis in phasor model AC power analysisAC power analysis Magnetically coupled circuitsMagnetically coupled circuits Concept of balanced three-phase circuitsConcept of balanced three-phase circuits
Basic Theory of Circuits, SJTUBasic Theory of Circuits, SJTU88
Topics covered:Topics covered:
Analysis of two-port networkAnalysis of two-port network network parameternetwork parameter Interconnection of networksInterconnection of networks Reciprocal networkReciprocal network analysis of the terminated two-port circuitanalysis of the terminated two-port circuit
Basic Theory of Circuits, SJTUBasic Theory of Circuits, SJTU99
Place of Electrical Circuits Place of Electrical Circuits in Modern Technology in Modern Technology
The design of the circuits has 2 main objectives: 1) To gather, store, process, transport, and present information.
2) To distribute and convert energy between various forms.
The study of circuits provides a foundation for areas of electrical engineering such as:
• Communication system
• Computer system
• Control system
• Electronics
• Electromagnetic
• Power systems
• Signal processing
Basic Theory of Circuits, SJTUBasic Theory of Circuits, SJTU1010
Motivation for doing this course
About the course
Circuit TheoryCircuit Analysis
Circuit Synthesis
Circuits(given)
Excitation(given)
Response(unknown)
Circuit Analysis
This is what we emphasize on,Since it provides the foundation for understanding the interaction of signal solution.
Circuits(unknown)
Excitation(given)
Response(given)
Circuit synthesis (design)
In contrast to analysis,a design problem may have no solution or several solutions,
As a student of SEIEE, you should :
1) Understand the main principles of how electrical equipment operates. So you can operate or maintain electrical systems.
2) Have a broad enough knowledge base to lead further study.
Basic Theory of Circuits, SJTUBasic Theory of Circuits, SJTU1111
Resistance circuits analysis
Dynamic circuits analysis
Sinusoidal steady state
The course includes:
Reference Books
1) Fundamentals of Electric Circuits Charles K Alexander TsingHua Uni Press (photocopy version)
2) The Analysis and Design of Linear Circuits Roland E.Thomas, Albert J.Rosa—2nd ed
3) Electrical Engineering Principles and Applications Allan R.Hambley ---2nd ed
4) 电路分析基础 李瀚荪 第三版
5) 电路 邱关源 第四版
6) Electric Circuits Joseph Edminister, Mahmood Nahvi -----3rd ed
Basic Theory of Circuits, SJTUBasic Theory of Circuits, SJTU 1212
Chapter 1Chapter 1Fundamental KnowledgeFundamental Knowledge
Basic Theory of Circuits, SJTUBasic Theory of Circuits, SJTU1313
What is covered in What is covered in Chapter 1:Chapter 1:
Circuit and Circuit modelCircuit and Circuit modelCircuit VariablesCircuit VariablesCircuit ElementsCircuit Elements
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Circuit and Circuit ModelCircuit and Circuit Model
Actual electrical component:Actual electrical component: a battery or a light a battery or a light bulbbulb
• Ideal circuit component: a mathematical model of an actual electric component.
Actual electrical component
Ideal circuit component
Emphasize the main character
Neglect the left characters
R1
Vs
Rs
Circuit Model
Basic Theory of Circuits, SJTUBasic Theory of Circuits, SJTU1515
Circuit model: A commonly used mathematical model for electric system.
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i1=i2 ; V is certain
Actual scale of the circuit is much smaller than the wavelength relating to the running frequency of the circuit.
Circuit Type:
• Linear----Nonlinear
• Time invariant----Time variant
• Passive----Active
• Lumped----Distributive
Lumped element Lumped circuit
i2
-V+
i1
Basic Theory of Circuits, SJTUBasic Theory of Circuits, SJTU1717
Circuit VariablesCircuit Variables Electric current is the time rate of change of charge, measured in amperes (A).
A direct current (DC) is a current that remains constant with time. (I)
An alternating current (AC) is a current that varies sinusoidally with time.
Sort
Where q is charge in coulombs(C)dt
dqi
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Reference direction
i >0 means the real direction is same to the reference direction
i <0 means the real direction is opposite to the reference direction
i
Basic Theory of Circuits, SJTUBasic Theory of Circuits, SJTU1919
Circuit VariablesCircuit VariablesVoltage (or potential difference) is the energy required to move a unit charge through an element, measured in volts(V).
Reference direction or voltage polarity
V>0 means the real polarity is same to the reference polarity
V<0 means the real polarity is opposite to the reference polarity
Where w is energy in joules(J)
And q is charge in coulombs(C)dq
dwv
-V+
Basic Theory of Circuits, SJTUBasic Theory of Circuits, SJTU2020
passive sign convention
Passive sign convention is satisfied when current enters through the positive polarity of the voltage.
Unless stated, we will follow the passive sign convention throughout this course.
-V+
i
Basic Theory of Circuits, SJTUBasic Theory of Circuits, SJTU2121
Circuit VariablesCircuit Variables Power is the time rate of expending or absorbing energy.
Measured in watts(W)
P=VI in a DC circuit
using passive sign convention
Power absorbed = - Power supplied
The algebraic sum of power in a circuit, at any instant of time, must be zero.
dt
dwp
vip
Basic Theory of Circuits, SJTUBasic Theory of Circuits, SJTU2222
Reference polaritiesReference polarities for power for power using passive sign conventionusing passive sign convention
P > 0 absorbing power
P < 0 releasing or supplying power
Examples
Law of conservation of energy must be obeyed in any electric circuit.
Power absorbed = - Power supplied 0p
Basic Theory of Circuits, SJTUBasic Theory of Circuits, SJTU2323
Energy is the capacity to do work, measured in joules(J)
The energy absorbed or supplied by an element from time t0 to time t is
t
t
t
tvidtpdtw
0 0
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Circuit ElementsCircuit Elements
Passive elements: resistors, capacitors, and inductors
Active elements: source, operational amplifiers
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Voltage and Current Sources Voltage and Current Sources
An ideal independent source is an active element that provides a specified voltage or current that is completely independent of other circuit variables.
Symbols for independent voltage source Symbols for independent current source
The voltage is determined by itself but the current through it is determined by the outside circuit
independent sources
dependent sources
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Note: 2 or more voltage sources with different value are not permissible to be connected in parallel
2 or more current sources with different value are not permissible to be connected in series
Voltage sources connected in series is equivalent to one voltage source
Current sources connected in parallel is equivalent to one current source
A voltage source connected to any branch in parallel is equivalent to itself
A current source connected to any branch in series is equivalent to
itself
Basic Theory of Circuits, SJTUBasic Theory of Circuits, SJTU2727
An ideal dependent (or controlled) source is an active element in which the source quantity is controlled by another voltage or current.
Symbols for a) dependent voltage sources b) dependent current sources
There are a total of four variations
1. A voltage –controlled voltage source (VCVS)
2. A current –controlled voltage source (CCVS)
3. A voltage –controlled current source (VCCS)
4. A current –controlled current source (CCCS)
Basic Theory of Circuits, SJTUBasic Theory of Circuits, SJTU2828
What is the difference between independent and dependent sources?
VCVS
V1 V1 I1
CCVS
I1
g
VCCS
V1 V1
CCCS
I1
I1
Basic Theory of Circuits, SJTUBasic Theory of Circuits, SJTU2929
Resistors Resistors The circuit element used to model the current –resisting behavior of a material is the resistor.
Resistance is the capacity of materials to impede the flow of current.
The resistance R of an element denotes its ability to resist the flow of electric current; it is measured in ohms (Ω)
Symbol: R1
1k
Basic Theory of Circuits, SJTUBasic Theory of Circuits, SJTU3030
i
u
i
u
t1t2
u
i
i
u
i
u
t1t2
u
i
Linear Time Invariant Linear Time variant
Nonlinear Time Invariant Nonlinear Time Variant
Open Circuit
Short Circuit
The i-v characteristic
Basic Theory of Circuits, SJTUBasic Theory of Circuits, SJTU3131
Linear Resistor: The resistance of the idea resistor is constant and its value does not vary over time.
The relation between voltage and current. (VAR)
v
i
V=Ri (passive sign convention)
-------Ohm’s Law
Since the value of R can range from zero to infinity, it is important that we consider the two extreme possible value of R:
R=0-------is called a short circuit; V=0;
R=∞------is called an open circuit, I=0;
Basic Theory of Circuits, SJTUBasic Theory of Circuits, SJTU3232
Conductance G is the reciprocal of the resistance, measured in siemens (s)
Power : P=vi (passive sign convention)
always absorbs power from the circuit
Other methods of expressing :
About nonlinear resistor ( diode, triode)
RG
1
G
iGvvip
R
vRivip
22
22