Department of Electronic Engineering BASIC ELECTRONIC ENGINEERING EE 2301 BASIC ELECTRONIC CIRCUIT

Department of Electronic Engineering BASIC ELECTRONIC ENGINEERING INSTRUCTOR: DR. ANGUS WU OFFICE: G6352 PHONE: URL: ID: ee2301 passwd: ee2301

Department of Electronic Engineering BASIC ELECTRONIC ENGINEERING LECTURE 1

Department of Electronic Engineering BASIC ELECTRONIC ENGINEERING Fundamentals Charge, Current, Voltage Ohm’s Law and Power Series Circuits and Kirchhoff’s Voltage Law Parallel Circuits and Kirchholf’s Current Law Resistive Circuits Circuit Analysis Techniques

Department of Electronic Engineering BASIC ELECTRONIC ENGINEERING Charge

Department of Electronic Engineering BASIC ELECTRONIC ENGINEERING The Starting Point: Elements, Atoms and Charge

Department of Electronic Engineering BASIC ELECTRONIC ENGINEERING

Department of Electronic Engineering BASIC ELECTRONIC ENGINEERING Charge –Force that causes two particles to be attracted to, or repelled from, each other –Two types – positive and negative –Atom – proton (positive), electron (negative), neutron (electrically neutral)

Department of Electronic Engineering BASIC ELECTRONIC ENGINEERING Attraction and Repulsion - Like charges repel each other and opposite charges attract each other Ions –Outside force can cause an electron to leave its orbit -atom is referred to as a positive ion –Outside force can cause an atom to gain an electron -atom is referred to as a negative ion Free Electrons –An electron that is not bound to any particular atom –Can neutralize a positive ion

Department of Electronic Engineering BASIC ELECTRONIC ENGINEERING

Department of Electronic Engineering BASIC ELECTRONIC ENGINEERING Current

Department of Electronic Engineering BASIC ELECTRONIC ENGINEERING Current Current – the directed flow of charge through a conductor –Thermal energy (heat) is sufficient to free electrons in copper –Free electron motion is random unless outside force is applied

Department of Electronic Engineering BASIC ELECTRONIC ENGINEERING Current Represented by the letter i (for intensity) Measured in charge per unit time where i = the intensity of the current dq = the amount of charge dt= the time (in seconds) required for the charge (dq) to pass

Department of Electronic Engineering BASIC ELECTRONIC ENGINEERING Current Coulomb (C) – represents the total charge of approximately 6.25 x electrons Unit of Current – Ampere (A) = 1 coulomb/second Example: 3 coulombs of charge pass a point in a wire every two seconds. Calculate current.

Department of Electronic Engineering BASIC ELECTRONIC ENGINEERING Electrical Current Electrical current is the time rate of flow of electrical charge through a conductor or circuit element. The units are amperes (A), which are equivalent to coulombs per second (C/s).

Department of Electronic Engineering BASIC ELECTRONIC ENGINEERING Electrical Current

Department of Electronic Engineering BASIC ELECTRONIC ENGINEERING Electrical Current Electron Flow Versus Conventional Current Insert Figure 1.10

Department of Electronic Engineering BASIC ELECTRONIC ENGINEERING

Department of Electronic Engineering BASIC ELECTRONIC ENGINEERING Direct Current Alternating Current When a current is constant with time, we say that we have direct current, abbreviated as dc. On the other hand, a current that varies with time, reversing direction periodically, is called alternating current, abbreviated as ac.

Department of Electronic Engineering BASIC ELECTRONIC ENGINEERING Figure 4.17, 4.18

Department of Electronic Engineering BASIC ELECTRONIC ENGINEERING

Department of Electronic Engineering BASIC ELECTRONIC ENGINEERING.

Department of Electronic Engineering BASIC ELECTRONIC ENGINEERING

Department of Electronic Engineering BASIC ELECTRONIC ENGINEERING

Department of Electronic Engineering BASIC ELECTRONIC ENGINEERING Two different methods of labeling the same current. (a,b) Incomplete, improper, and incorrect definitions of a current. (c) the correct definition of i 1 (t).

Department of Electronic Engineering BASIC ELECTRONIC ENGINEERING Current Insert Figure 1.11

Department of Electronic Engineering BASIC ELECTRONIC ENGINEERING Voltage

Department of Electronic Engineering BASIC ELECTRONIC ENGINEERING Voltage The voltage associated with a circuit element is the energy transferred per unit of charge that flows through the element. The units of voltage are volts (V), which are equivalent to joules per coulomb (J/C).

Department of Electronic Engineering BASIC ELECTRONIC ENGINEERING Voltage Voltage – a “difference of potential” that generates the directed flow of charge (current) through a circuit Insert Figure 1.12

Department of Electronic Engineering BASIC ELECTRONIC ENGINEERING

Department of Electronic Engineering BASIC ELECTRONIC ENGINEERING Voltage Often referred to as electromotive force (emf) Unit of Voltage – volt (V) = 1 joule/coulomb Volt – the difference of potential that uses one joule of energy to move one coulomb of charge.

Department of Electronic Engineering BASIC ELECTRONIC ENGINEERING

Department of Electronic Engineering BASIC ELECTRONIC ENGINEERING

Department of Electronic Engineering BASIC ELECTRONIC ENGINEERING (a, b) These are inadequate definitions of a voltage. (c) A correct definition includes both a symbol for the variable and a plus- minus symbol pair. (a, b) Terminal B is 5 V positive with respect to terminal A; (c,d) terminal A is 5 V positive with respect to terminal B.

Department of Electronic Engineering BASIC ELECTRONIC ENGINEERING

Department of Electronic Engineering BASIC ELECTRONIC ENGINEERING Ideal voltage sources Various representations of an electrical system

Department of Electronic Engineering BASIC ELECTRONIC ENGINEERING Symbol for ideal current source

Department of Electronic Engineering BASIC ELECTRONIC ENGINEERING Ohm’s Law and Power

Department of Electronic Engineering BASIC ELECTRONIC ENGINEERING Ohm’s Law German Physicist – George Simon Ohm –Found that current is inversely proportional to resistance for a given voltage –Known as Ohm’s law The Relationship Between Current and Voltage The Relationship Between Current and Resistance

Department of Electronic Engineering BASIC ELECTRONIC ENGINEERING Basic Circuit Calculations Using Ohm’s Law to Calculate Current where R= the circuit resistance V = the applied voltage

Department of Electronic Engineering BASIC ELECTRONIC ENGINEERING Basic Circuit Calculations Using Ohm’s Law to Calculate Voltage where I = the circuit current R = the circuit resistance

Department of Electronic Engineering BASIC ELECTRONIC ENGINEERING Basic Circuit Calculations Using Ohm’s Law to Calculate Resistance where V = the circuit voltage I = the circuit current

Department of Electronic Engineering BASIC ELECTRONIC ENGINEERING Resistance Element

Department of Electronic Engineering BASIC ELECTRONIC ENGINEERING Power Power – the amount of energy used per unit time Unit of Power – Watt (W) = 1 joule/second Calculating Power where P = the power used, in watts (W) V= the applied voltage, in volts (V) I = the generated current, in amperes (A) P = IV

Department of Electronic Engineering BASIC ELECTRONIC ENGINEERING Power Other Power Equations –Use IR in place of V –Use V/R in place of I

Department of Electronic Engineering BASIC ELECTRONIC ENGINEERING If the current arrow is directed into the “ +” marked terminal of an element, then p = vi yields the absorbed power. A negative value indicates that power is actually being generated by the element. If the current arrow is directed out of the “ +” terminal of an element, then p = vi yields the supplied power. A negative value in this case indicates that power is actually being absorbed instead of generated.

Department of Electronic Engineering BASIC ELECTRONIC ENGINEERING Passive Sign Conversion

Department of Electronic Engineering BASIC ELECTRONIC ENGINEERING POWER AND ENERGY instantaneous power

Department of Electronic Engineering BASIC ELECTRONIC ENGINEERING Power Power and Heat –Resistors and other components convert energy to heat (transducer) –If power rating is exceeded, the component will keep getting hotter and be destroyed –Common guideline – select a component with twice the required power-dissipation capability

Department of Electronic Engineering BASIC ELECTRONIC ENGINEERING Power Efficiency – the ratio of a circuit or components output power to its input power where  = the efficiency, as a percentage P o = the output power P i = the input power

Department of Electronic Engineering BASIC ELECTRONIC ENGINEERING Miscellaneous Topics Resistor Tolerance –Resistor value falls within a range –Circuit current also falls within a range

Department of Electronic Engineering BASIC ELECTRONIC ENGINEERING Miscellaneous Topics Circuit Loads –Source – supplies the power –Load – absorbs (uses) the power –Full Load – one that draws the maximum current

Department of Electronic Engineering BASIC ELECTRONIC ENGINEERING Practical Voltage Source

Department of Electronic Engineering BASIC ELECTRONIC ENGINEERING Practical Current Source

Department of Electronic Engineering BASIC ELECTRONIC ENGINEERING Circuit Topology Fundamental

Department of Electronic Engineering BASIC ELECTRONIC ENGINEERING Definition of a branch

Department of Electronic Engineering BASIC ELECTRONIC ENGINEERING Definitions of node and supernode

Department of Electronic Engineering BASIC ELECTRONIC ENGINEERING ( a) A circuit containing three nodes and five branches. (b) Node 1 is redrawn to look like two nodes; it is still one node.

Department of Electronic Engineering BASIC ELECTRONIC ENGINEERING Definition of a loop Definition of a mesh

Department of Electronic Engineering BASIC ELECTRONIC ENGINEERING Series Circuits and Kirchhoff’s Voltage Law

Department of Electronic Engineering BASIC ELECTRONIC ENGINEERING Voltage Relationships: Kirchhoff’s Voltage Law Kirchhoff’s Voltage Law –The sum of the component voltages in a series circuit must equal the source voltage 1840 – German Physicist, Gustav Kirchhoff –Actual wording – The algebraic sum of the voltages around a closed loop is zero –The following equation takes polarity into account

Department of Electronic Engineering BASIC ELECTRONIC ENGINEERING Kirchhoff’s Voltage Law, Example: V S = +10V, V 1 = +2V, V 2 = +8V

Department of Electronic Engineering BASIC ELECTRONIC ENGINEERING Series Circuit Characteristics Series Circuit – a circuit that contains only one current path

Department of Electronic Engineering BASIC ELECTRONIC ENGINEERING (a) Series combination of N resistors. (b) Electrically equivalent circuit.

Department of Electronic Engineering BASIC ELECTRONIC ENGINEERING Series Circuit Characteristics Total Series Resistance where R T = the total circuit resistance R n = the highest-numbered resistor in the circuit

Department of Electronic Engineering BASIC ELECTRONIC ENGINEERING Series Circuit Characteristics Current Characteristics – the current at any point in a series circuit must equal the current at every other point in the circuit Insert Figure 4.5

Department of Electronic Engineering BASIC ELECTRONIC ENGINEERING Series Circuit Characteristics Voltage Characteristics where V S = the source (or total) voltage V n = the voltage across the highest numbered resistor in the circuit

Department of Electronic Engineering BASIC ELECTRONIC ENGINEERING (a) Series connected voltage sources can be replaced by a single source. (b) Parallel current sources can be replaced by a single source.

Department of Electronic Engineering BASIC ELECTRONIC ENGINEERING Examples of circuits with multiple sources, some of which are “illegal” as they violate Kirchhoff’s laws.

Department of Electronic Engineering BASIC ELECTRONIC ENGINEERING Series Circuit Characteristics Power Characteristics where P S = the source (or total) voltage P n = the power that is dissipated across the highest numbered resistor in the circuit

Department of Electronic Engineering BASIC ELECTRONIC ENGINEERING Series Circuit Characteristics Insert Figure 4.10

Department of Electronic Engineering BASIC ELECTRONIC ENGINEERING Voltage References Voltage References - Circuits have a point that serves as the 0 V reference (ground) Insert Figure 4.12

Department of Electronic Engineering BASIC ELECTRONIC ENGINEERING Voltage Divider The Voltage Divider Relationship –Voltage Divider – often used to analyze a series circuit where R n = the resistor of interest V n = the voltage drop across R n (where n is the component number)

Department of Electronic Engineering BASIC ELECTRONIC ENGINEERING An illustration of voltage division. We may find v 2 by applying KVL and Ohm’s law: so Thus, or For a string of N series resistors, we may write:

Department of Electronic Engineering BASIC ELECTRONIC ENGINEERING Source Resistance: A Practical Consideration –Ideal Voltage Source – maintains a constant output voltage regardless of the resistance of its load –Real Voltage Source – internal resistance causes a decrease in load resistance results in a decrease in the source voltage

Department of Electronic Engineering BASIC ELECTRONIC ENGINEERING Insert Figure 4.20 Source Resistance: A Practical Consideration (Continued)

Department of Electronic Engineering BASIC ELECTRONIC ENGINEERING Maximum Power Transfer Theorem maximum power transfer from a voltage source to its load occurs when the load resistance is equal to the source resistance

Department of Electronic Engineering BASIC ELECTRONIC ENGINEERING Series-Connected Voltage Sources Series-Aiding Voltage Sources – the total voltage equals the sum of the voltages Series-Opposing Voltage Sources – the total voltage equals the difference of the voltages

Department of Electronic Engineering BASIC ELECTRONIC ENGINEERING Earth Ground Versus Chassis Ground Insert Figure 4.28

Department of Electronic Engineering BASIC ELECTRONIC ENGINEERING Parallel Circuits and Kirchholf’s Current Law

Department of Electronic Engineering BASIC ELECTRONIC ENGINEERING Current Relationships: Kirchhoff’s Current Law Kirchhoff’s Current Law – the algebraic sum of the currents entering and leaving a point must equal zero –In other words, the total current leaving a point must equal the total current entering that point

Department of Electronic Engineering BASIC ELECTRONIC ENGINEERING

Department of Electronic Engineering BASIC ELECTRONIC ENGINEERING Parallel Circuit Characteristics Parallel Circuit – a circuit that provides more than one current path between any two points Insert Figure 5.1

Department of Electronic Engineering BASIC ELECTRONIC ENGINEERING Parallel Circuit Characteristics Current Characteristics where I n = the current through the highest-numbered branch in the circuit

Department of Electronic Engineering BASIC ELECTRONIC ENGINEERING Parallel Circuit Characteristics Voltage and Current Values –Voltage across each component is equal –Current through each branch is determined by the source voltage and the resistance of the branch.

Department of Electronic Engineering BASIC ELECTRONIC ENGINEERING Parallel Circuit Characteristics Resistance Characteristics – the total circuit resistance is always lower than any of the branch resistance values Insert Figure 5.5

Department of Electronic Engineering BASIC ELECTRONIC ENGINEERING Parallel Circuit Characteristics Power Characteristics –Total Power – sum of the power dissipation values for the individual components –The lower value of the branch resistance, the higher percentage of the total power it dissipates (opposite that of series circuits)

Department of Electronic Engineering BASIC ELECTRONIC ENGINEERING Parallel Circuit Characteristics Insert Figure 5.6

Department of Electronic Engineering BASIC ELECTRONIC ENGINEERING Parallel Resistance Relationships Conductance (G) –A measure of the ability of a component or circuit to conduct –Total conductance (G T ) in a parallel circuit equals the sum of the branch conductance values where G n = the conductance of the highest-numbered branch in the circuit

Department of Electronic Engineering BASIC ELECTRONIC ENGINEERING Parallel Resistance Relationships Calculating Total Resistance: The Reciprocal Method Proof – Using KVL and KCL

Department of Electronic Engineering BASIC ELECTRONIC ENGINEERING (a) A circuit with N resistors in parallel. (b) Equivalent circuit. Beginning with a simple KCL equation, or Thus, A special case worth remembering is

Department of Electronic Engineering BASIC ELECTRONIC ENGINEERING Parallel Resistance Relationships Calculating Total Resistance: The Product- Over-Sum Method

Department of Electronic Engineering BASIC ELECTRONIC ENGINEERING Current Sources a source that is designed to provide an output current value that remains relatively constant over a wide range of load resistance values Insert Figure 5.12

Department of Electronic Engineering BASIC ELECTRONIC ENGINEERING Current Dividers Current Dividers – the source current is divided among the branches Insert Figure 5.15

Department of Electronic Engineering BASIC ELECTRONIC ENGINEERING An illustration of current division. The current flowing through R 2 is For a parallel combination of N resistors, the current through R k is or

Department of Electronic Engineering BASIC ELECTRONIC ENGINEERING Practical Current Sources: The Effects of Source Resistance –Ideal Current Source – constant current and infinite internal resistance –Real Current Source – current varies for a change in load resistance and internal resistance is not infinite –Internal resistance is usually much greater than the load resistance

Department of Electronic Engineering BASIC ELECTRONIC ENGINEERING Maximum Power Transfer – For a fixed value of R S, maximum power transfer occurs when R L = R S

Department of Electronic Engineering BASIC ELECTRONIC ENGINEERING Series-Parallel Circuits

Department of Electronic Engineering BASIC ELECTRONIC ENGINEERING Series-Parallel Circuits Connecting Series Circuits in Parallel Insert Figure 6.3

Department of Electronic Engineering BASIC ELECTRONIC ENGINEERING Series-Parallel Circuits Connecting Parallel Circuits in Series Insert Figure 6.5

Department of Electronic Engineering BASIC ELECTRONIC ENGINEERING Analyzing Series-Parallel Circuits

Department of Electronic Engineering BASIC ELECTRONIC ENGINEERING KIRCHHOFF’S VOLTAGE LAW Formal Expression

Department of Electronic Engineering BASIC ELECTRONIC ENGINEERING KIRCHHOFF’S VOLTAGE LAW The algebraic sum of the voltages equals zero for any closed path (loop) in an electrical circuit. In a closed path, each element is encountered only once.

Department of Electronic Engineering BASIC ELECTRONIC ENGINEERING Define the voltage for each component

Department of Electronic Engineering BASIC ELECTRONIC ENGINEERING

Department of Electronic Engineering BASIC ELECTRONIC ENGINEERING Loop 1 -Va + Vb + Vc =0 Loop 2 -Vc – Vd + Ve =0 Loop 3 -Ve + Vd – Vb + Va = 0 Va is ‘+’ in loop 3 But ‘-’ in loop 1

Department of Electronic Engineering BASIC ELECTRONIC ENGINEERING VOLTAGE SOURCE AND CURRENT SOURCE

Department of Electronic Engineering BASIC ELECTRONIC ENGINEERING

Department of Electronic Engineering BASIC ELECTRONIC ENGINEERING Why ? As I = V/R, R = 0, implies, I is infinitive Power = VI = infinitive? Theoretical correct but not in real world.

Department of Electronic Engineering BASIC ELECTRONIC ENGINEERING

Department of Electronic Engineering BASIC ELECTRONIC ENGINEERING

Department of Electronic Engineering BASIC ELECTRONIC ENGINEERING

Department of Electronic Engineering BASIC ELECTRONIC ENGINEERING Symbols for dependent sources

Department of Electronic Engineering BASIC ELECTRONIC ENGINEERING KIRCHHOFF’S CURRENT LAW Formal Expression

Department of Electronic Engineering BASIC ELECTRONIC ENGINEERING KIRCHHOFF’S CURRENT LAW The net current entering a node is zero. Alternatively, the sum of the currents entering a node equals the sum of the currents leaving a node.

Department of Electronic Engineering BASIC ELECTRONIC ENGINEERING (a)i a = 1A + 3A = 4A (b)i b + 1 A + 3 A = 2 A, i b = - 2A, that is flowing outward (c)i c + 4 A + 1 A + 3 A = 0, i c = - 8 A, flows outward too