Electromagnetism, Electricity

And Digital Electronics

By

Engr. Jorge P. Bautista

Course Outline

I. Theory of Electrons and Electricity

II. Resistor and other passive elements

III. Ohm’s Law and Electric Circuits

IV. Theory of Magnetism

V. Diode and other Electronic Devices

VI. Logic Gates and flip-flops

VII. Combinational and sequential circuits

Text and References

• Digital Design by Mano• Electronic Devices by Floyd• Engineering Circuit Analysis by Hayt• Introduction to Electric Circuits by Dorf• Introduction to Digital Circuits by Bogart

Theory of Electrons

Principles of Electrons:

Electrons orbit the nucleus of an atom at certain distances from the nucleus. Electrons near the nucleus have less energy than those in more distant orbits.

Bohr’s Atomic Theory of an atom

An atom consist of a nucleus in which it consist of a neutron and a proton in which electrons orbit around it.

Shells of an Atom

In an atom, orbits are group into energy bands know as shells. Each shell has a fixed maximum number of electrons at permissible energy levels. The shells are designated as K,L,M,N, and so on. The outermost shell is know as valence shell and the electrons in this shell are called valence electrons. These valence electrons contribute to chemical reactions and bonding.

Shells of orbital Electrons in an Atom

s p d f g Total

K 2 2

L 2 6 8

M 2 6 10 18

N 2 6 10 14 32

O 2 6 10 14 18 50

Parts of an Atom

Proton – positively charge particle

Electron – negatively charge particle

Neutron – neutral charge particle or no charge at all.

Ionization

Ionization – the process of losing a valence electrons.

Ion – the resulting positively charge atom

Free electrons – the escaped valence electron.

Positive ion – ions that loses an electron

Negative ion – ions that gained an electron

What are insulators, conductors and semi-conductors?

Insulator – name given to materials that do not conduct electricity. They have less than 8 free electrons

Conductor – name given to materials that is a good conductor of electricity. They have many free electrons

Semiconductor – materials having 8 valence electrons.

Some insulators and conductors

*Insulator *ConductorGlass GoldPorcelain SilverMica CopperRubber AluminumAsbestos ZincParaffin TinPaper LeadAir iron

WIRE SIZES

AWG gauge

Diameter, mm

Ohms per Km

Ampacity

0 8.2524 0.3224 245A

1 7.3482 0.4063 211A

22 0.6451 52.9392 7A

24 0.5105 84.1976 3.5A

28 0.3200 212.872 1.4A

What is Electricity?Electricity is• the flow of electrons from an area high in electron

excess to one of lower electron content.• the flow of energy in a wire (similar to the flow of

water in a pipe) that is invisible, that causes the wire to become hot , causes a magnetic field to develop around the wire and can be put to work driving pumps, blowers, fans and so forth.

• Electricity cannot be generated. It can neither be created nor destroyed. It can, however, be forced to move and thus transmit power or produce electrical phenomena.

Two types of electricity:• Static electricity – electricity at rest• Dynamic electricity – electricity in motion

Common Sources of Electrical energy or Power.

1. Battery – a single unit capable of producing DC voltage by converting chemical energy into electrical energy.

2. Dynamo – a machine that converts mechanical energy to electrical energy and vice versa.

3. Motor – transformation from electrical energy to mechanical energy.

4. Generator – transformation from mechanical energy to electrical energy.

5. Solar energy – it converts solar energy from the sun through the use of solar cells.

Alternating Current (AC) and Direct Current (DC)

Direct current or DC is the first type of current because it is easy to produce. This current always flows in one direction. Its disadvantage is that it has an excessive voltage drop and power loss in the power lines for a long distance. Batteries are common sources of direct current.

Alternating current is the solution to the problem of DC. AC allows the flow of current in two directions. Today, it is possible to step up electricity to a power station, transmit it to any distant place and step it down for consumption. A transformer is the device used for stepping up and stepping down AC voltage.

Graphical Representation of a DC

Graphical Representation of an AC

How Electricity is Delivered to a Customer

What is electrical energy and power?

• Electrical Energy – the capacity to do electrical work

• Unit: watt-sec, kilowatt-hour, joule • W = P x t• Where: W = energy• P = power• t = time

• Conversion factor: 1 joule = 107 ergs

• Electric Power – the rate of doing electrical work or it is the rate at which electrical energy is converted to other forms of energy.

• Unit: joule/sec, watt• P = work/time = EI = E2/R = I2R• Where E = voltage• I = current• R = resistance

What is voltage?

Voltage - (potential Difference) or (electromotive force) – the force or pressure which makes electrons moves or tends to move from atom to atom along the wire.

Unit: volts

What are current and resistance?

Current – the rate of flow of electrons per unit of time. It can be direct current or alternating current.

Unit: Ampere

Resistance– the capability of the resistor to limit the flow of current and reduce the amount of voltage in a circuit.

Unit: ohms,

Ohm’s Law

The current is directly proportional to the voltage across the resistance and inversely proportional to the resistance.

V

I = -----

R

Power Relationship: P = VI

Mathematical PrefixesGiga = x109

Mega = x106

Kilo = x103

milli = x10-3

micro = x10-6

nano = x10-9

pico = x10-12

Conversion to Prefixes and Scientific Notations

1. 25000000V 2. 0.0000067A3. 1250000 meters4. 0.005 liters5. 2.4x103 meters6. 33x10-6watts7. 0.00045 A8. 6.6x106 Ω

EXERCISES

VOLTAGE CURRENT RESISTANCE POWER

24A 10Ω

30V 3Ω

10A 260W

1.2Ω 120W

12V 300W

Basic Electrical Variables

Variable Symbol UnitTime t secCharge Q CoulombCurrent I AmpereVoltage V VoltsPower P WattsEnergy W JouleResistance R OhmsConductance G Seimens, mho

Examples

1. A simple circuit has 12V and a resistance of 4.7K. Determine the current and power of the circuit.

2. The output current of a certain integrated circuit is 6mA and it is flowing into a resistance of 5K. Determine the voltage across the resistance.

3. Determine the hot resistance of a 60watts bulb operated from an effective voltage of 120V.

4. The power dissipated in a certain resistance is 100watts and the current is 4A. Determine the resistance.

5. Assume that a family leaves a 60watts light bulb on for a duration of a two weeks trip. If electricity cost 9 cents per kilowatt-hour, determine the cost incurred.

Assignment no. 1I. Research on the following scientist and state

what invention he contributed in the field of electronics

1. Cuneus and Muschenbrock

2. Benjamin Franklin

3. Charles Augustus Coulomb

4. Luigi Galvani

5. Alessandro Volta

6. Hans Christian Oersted

7. Andre Marie Ampere

8. Georg Simon Ohm9. Michael Faraday10. Karl Friedrich Gauss and Wilhelm Eduard Weber11. Joseph Henry12. Heinrich Lenz13. Samuel Finley Breese Morse14. Gustav Robert Kirchhoff15. James Clerk Maxwell16. Joseph Wilson Swan17. Thomas Alva Edison18. Heinrich Rudolf Hertz19. Nikola Tesla20. Guglielmo Marconi

21. Albert Einstein

22. Shockley, Bardeen and Brattain

23. Jack Kilby

24. Robert Norton Noyce

25. Seymour Cray

II. Complete the Table below, show your solutionsresistance current voltage power

2.4A 220W

22Ω 13.75V

10mA 12V

100Ω 3W

III. Problem Solving1. What is the power in a circuit if the

secondary transformer rated at 12V, 2A?2. How much is the power loss of 100Ω

resistance, which consumes current of 10A?

3. How much current is flowing in a 1KΩ resistor with an input voltage of 12V?

4. How much resistance is needed to absorbed a current of 2.5mA with a voltage of 3V?

Electronics Test InstrumentsElectronics test instruments are crucial instruments

that are often use for troubleshooting, repairing and analyzing the operation of a specific device. The most frequently measured parameters are the voltage, resistance and current.

The multi-tester or multi-meter or sometimes called VOM(Voltmeter, Ohmmeter, Milliammeter) is best instrument that can measure voltage, resistance and current. But this instrument measures the numerical value, not the actual waveform, which is also important to know when troubleshooting and determining the frequency of the signal.

Analog Multi-tester

The analog multi-tester has a moving coil assembly which is characterized by a needle pointer. The advantage of analog multi-tester over digital multitester is a resistance test in testing electronic components such as capacitor and transistor.

Steps in Using Analog Multi-tester1. Connect the test probe to the appropriate jack.

The red probe to the + jack and black probe to the (-) common jack.

2. Check is the pointer rest exactly at the zero position or infinite position at the ohmmeter range. If not adjust the zero corrector screw.

3. Check the accuracy of the ohmmeter by touching the two test probe. Set the multitester to x1 ohm or x10 ohms selector range. Hold the two test probe simultaneously. The pointer should not deflect when holding the two test probe. If the pointer deflects, the ohmmeter range is defective.

4. Check the probes if they are OK. Set the multi-tester to corresponding selector resistance range. Short the two probes lead together. The pointer should deflect towards zero ohm reading. Adjust the ohm adjustment if the pointer could not rest exactly at “0” ohm reading. If nothing happen the possible cause is low powered battery

Resistance Measurement

Select the desired resistance range scale with the selector switch. Read the pointer and multiply by the selected range.

DC/AC Voltage Measurement

Set the selector knob to the proper scale range. The chosen scale range must be higher than the anticipated voltage to be measured.

DC/AC Current Measurement

The ammeter scale is the same as the voltmeter scale. Apply the same procedure in measuring voltage. However, in current measurement , the meter must be connected in series with the circuit. Unlike in measuring voltage, the connection is parallel.

Advantages of Digital over Analog

1. More accurate

2. It draws essentially no energy from the circuit being measured and hence will not affect the measured quantity

3. Some are featured with autoranges that change the scale automatically providing the correct read out without having to change manually.

Resistor Color Codedesignation 4 bands 5 bands 6 bands

1st band Significant figure

Significant figure

Significant figure

2nd band Significant figure

Significant figure

Significant figure

3rd band Multiplier Significant figure

Significant figure

4th band tolerance Multiplier Multiplier

5th band tolerance tolerance

6th band Temp coef

Resistor Color CodeColor SF multiplier TOL TC

Black 0 1

Brown 1 10 +/- 1% 100

Red 2 100 +/- 2% 50

Orange 3 1000 15

Yellow 4 10000 25

Green 5 100000 +/- 0.5%

Con’t

Blue 6 10 6 +/- 0.25% 10

Violet 7 10 7 +/- 0.1% 5

Grey 8 10 8 +/- 0.05%

White 9 10 9 1

Gold 10 -1 +/- 5%

Silver 10 -2 +/- 10%

Exercises Decode the following resistor color.1. red, blue, violet, green2. Blue, black, red, red3. Yellow, red, orange, silver4. Blue, black, black, red, red5. Green, red, red, green, blue6. Grey, green, silver, green7. Yellow, green, black, white, gold8. Blue, green, violet, red, orange, red

Two main categories of resistor

1. Linear resistor – those which obey ohms law.

2. Non-linear resistor – consist of three types

a. Light dependent resistor(LDR)- light sensitive

b. Thermistor – heat sensitive

c. Voltage dependent resistor

Linear Resistor

Potentiometer

Classification of ResistorAccording to type of material1. Carbon composition2. Carbon film3. Metal film4. Wire woundAccording to their tolerance5. General purpose, 5% or greater6. Semi-precision, 1% to 5%7. Precision, 0.5% to 1%8. Ultra-precision, less than 0.5%

Cross section of a resistor--

Assignment no. 2I. Research on the following and draw the

figure:

a. wattmeter

b. digital multimeter

II. Decode the following color coded resistor.

1. red, green, blue, violet

2. Yellow, green, silver, blue

3. Blue, yellow, orange, green, red

4. Red, blue, blue, red, orange

5. Violet, black, white, blue

Con’tIII. Find the color code of the given range of

resistances.

1. 4 bands 250Ω, +/-5%

2. 5 bands 4.32KΩ, +/-1%

3. 4 bands 270KΩ, +/-5%

4. 5 bands 619MΩ, +/-2%

5. 5 bands 356MΩ, +/-2%

Capacitor A device that stores electrons. The basic

capacitor is made up of two conductors separated by an insulator, or dielectric. Depending on how the capacitor is built, the dielectric can be made of paper, plastic, mica, ceramic, glass, vacuum or any other non conductive materials. Capacitor storing ability is measured in Farad. 1 Farad is approximately 6,280,000,000,000,000,000 electrons.

Capacitor Parts

Capacitor Diagram

Commonly Used Capacitor1. Electrolytic, as in previous image is

made of electrolyte, basically conductive salt in solvent.

2. Ceramic- constructed with materials such as titanium acid barium for dielectric.

3. Mylar(polyester Film)- this capacitor uses a thin polyester film as a dielectric.

4. Tantalum- made of tantalum pentoxide.

Mylar Capacitor

Capacitor code

Code Tolerance

J +/-5%

K +/- 10%

M +/-20%

C +/- 0.25%

Ceramics Capacitor

Exercises Find the capacitance of the given capacitor

1. mylar: 333M

2. Mylar: 665J

3. Ceramics: 44

4. Ceramics: 785

5. Ceramics: 2K

Series Parallel ResistorsSeries Resistors:Conditions:1. The total resistance of a series resistors

is the sum of the individual resistances.2. The total voltage of a series resistors is

the sum of individual voltages or voltage drops in each resistor.

3. The total current of a series resistors is equal to the individual current in each resistors.

R1 1kR2 1k

R3 1k

V1 5

R1 R2 R3

I1 I2 I3

+VR1- +VR2- +VR3-

It Vt

Equations:

Vt = VR1 + VR2 + VR3

= I1R1 + I2R2 + I3R3

Rt = R1 + R2 + R3

It = I1 = I2 = I3

Power Equation

Pt = P1 + P2 + P3

The total power in a series resistors is equal to the sum of the individual power in each resistor.

Example 1. Determine the total resistance, total current and

current and voltage in each resistor of the circuit below

R1

1k R2

1k

V1 5

15V

5 ohms

8 ohms

2. Find the total resistance, total current and voltage in each resistor.

R1 1kR2 1k

R3 1k

V1 520K 15K 30K

40V

3. Find Rx for the circuit shown below

R3

1kR4

1k

R5

1kT

P1

TP

2

Rt

Rx

= 33K ohms12K ohms

7.5K ohms

4. Find the value of the resistors in the given circuit if the total resistance is 100Ω.

R4 1kR5 1kR6 1kR7 1k

TP1

TP2

R 2R 3R 4R

5. Determine the voltage and power in each resistor below. Find the input voltage.

R3 1

k

R4 1

k

R5 1

k

V2 5

2.5K ohms

1.75K ohms

5K ohms

It = 1.6mA

Assignment no. 3 Find Vt,P1, R1, V2, P2, R3, V3 and Pt for the

circuit shown.

R6 1k

R7

1k

R8 1k

V3 5

Vt

V1 = 2.2V

R1, P1

V2,P2R2 = 4.8 ohms

R3,V3

P3 = 3.12W

2A

Parallel Resistors:

Conditions:

1. The total resistance is equal to the sum of the inverse of the resistances.

2. The total current is equal to the sum of the current in each resistor.

3. The voltages in each parallel resistor are equal.

R4 1

kR5

1k

R6 1

k

V2 5

Vt R1 R2 R3+VR1-

+VR2-

+VR3-

It I1 I2 I3

Equations

Vt = VR1 = VR2 = VR3

1 1 1 1

---- = ------ + ------ + -------

Rt R1 R2 R3

It = I1 + I2 + I3

Exercises

1. Find the total resistance of the given parallel resistors.

R1 1k

R2 1k

TP1TP2

Rt 5K 8.75K

2. Determine the total resistance of the given parallel resistors

R1 1k

R2 1k

TP1TP2

R3 1k

Rt 5K8.75K 10K

3. Find Rx for the parallel resistor below

R7 1k

R8 1k

R9 1k

V2 5

Vt1.5K Rx 2K

20V

4.1mA6.8mA

Assignment no. 4 4. Find the total resistance and current, voltage and power

in each resistor below

R4

1k R5

1k

R6

1k

V1 5

30V16 ohms 12 ohms 18 ohms

Series-parallel resistor

1. Find the total resistance of the circuit below:

R10 1k

R11 1

kR12

1kR1

3 1kTP3TP4R14 1k

Rt

12

8

7

3

10

2. Find the total resistance of the circuit below. Determine the total current and power.

R1 1k R2

1kR

3 1k

R4 1kR5

1k

V1 5R6 1k

15

10

8 4

2

224V

3. Find the total resistance of the circuit below.

R7 1k

R8

1k

R9 1k R10

1k R11 1k

R12

1k

V3 5

2 2

13

1.5

310V

4. Find the total resistance of the circuit below.

R13

1k

R14

1k

TP

1 TP

2R

15 1

k

R16

1k

Rt10 10

4

8

Assignment no. 51. Find the total current and resistance of the

circuit below.

V1 5

R1 1k

R2 1

k

R3 1

kR

4 1

k

R5 1k

R6 1

kR8 1k

4

2

3

36

4

4

20V

Magnetism• What is a magnet?• A magnet is an object made of certain materials which

create a magnetic field. Every magnet has at least one north pole and one south pole. By convention, we say that the magnetic field lines leave the North end of a magnet and enter the South end of a magnet. This is an example of a magnetic dipole ("di" means two, thus two poles). If you take a bar magnet and break it into two pieces, each piece will again have a North pole and a South pole. If you take one of those pieces and break it into two, each of the smaller pieces will have a North pole and a South pole. No matter how small the pieces of the magnet become, each piece will have a North pole and a South pole.

The ancient Greeks and Chinese discovered that certain rare stones, called lodestones, were naturally magnetized. These stones could attract small pieces of iron in a magical way, and were found to always point in the same direction when allowed to swing freely suspended by a piece of string. The name comes from Magnesia, a district in Thessaly, Greece

Things that uses magnet:

Headphones, stereo speakers, telephone receivers, phone ringers, microwave tubes, doorbell ringer solenoid, floppy disk recording and reading head, credit card, computer monitor deflection coil, computer hard drive recording, TV deflection coil, clothes washer and dryer, DVD spinner and head positioner, hard disk spinner, starter motor, A/C clutch, etc.

Ten facts about magnet• 1. North poles point north, south poles point south. • 2. Like poles repel, unlike poles attract. • 3. Magnetic forces attract only magnetic materials. • 4. Magnetic forces act at a distance. • 5. While magnetized, temporary magnets act like permanent

magnets. • 6. A coil of wire with an electric current flowing through it

becomes a magnet. • 7. Putting iron inside a current-carrying coil increases the

strength of the electromagnet. • 8. A changing magnetic field induces an electric current in a

conductor. • 9. A charged particle experiences no magnetic force when

moving parallel to a magnetic field, but when it is moving perpendicular to the field it experiences a force perpendicular to both the field and the direction of motion.

• 10. A current-carrying wire in a perpendicular magnetic field experiences a force in a direction perpendicular to both the wire and the field.

Types of magnets

Permanent magnet

Temporary magnets

Electromagnets

• Permanent Magnets• Permanent magnets are those we are most

familiar with, such as the magnets hanging onto our refrigerator doors. They are permanent in the sense that once they are magnetized, they retain a level of magnetism. As we will see, different types of permanent magnets have different characteristics or properties concerning how easily they can be demagnetized, how strong they can be, how their strength varies with temperature, and so on.

• Temporary Magnets• Temporary magnets are those which act like a

permanent magnet when they are within a strong magnetic field, but lose their magnetism when the magnetic field disappears. Examples would be paperclips and nails and other soft iron items.

• Electromagnets• An electromagnet is a tightly wound helical coil

of wire, usually with an iron core, which acts like a permanent magnet when current is flowing in the wire. The strength and polarity of the magnetic field created by the electromagnet are adjustable by changing the magnitude of the current flowing through the wire and by changing the direction of the current flow.

• Neodymium Iron Boron magnet = Nd2Fe14B or Nd15Fe77B8.

Coulomb’s law

The magnitude of the electrostatic force between two point electric charges is directly proportional to the product of the magnitudes of each of the charges and inversely proportional to the square of the total distance between the two charges.

k Q1Q2

F = -------------- where k = 8.99E9 Nm2/C2

r2

K = 1 / 4o

But = 8.854x10E-12

Examples1. Two charges of +1C each is separated at

a distance of 1meter. Determine the force of repulsion of the two charge.

2. Two balloons are charge with identical quantity of -6.25uC. They are separated with a distance of 66.67cm. Determine the force of repulsion of the two balloons.

3. Two charges +1.2uC and -2.4uC are separated with a distance of 2m. Determine the force of attraction of the two charges.

4. The force of attraction between a +2.2uC and an unknown charge is 1.2N. They are separated by 120cm distance. Find the charge of the other electron.

5. Given the figure below:

Find the total force of the two charges on charge -3.3uC. Which has greater force of attraction?

+2.2uC -3.3uC +4.5uC

21cm

45cm

Assignment no. 61. Two charges, -10uC and +15uC, are

acting on a force of attraction of 4.5N. Determine their distances.

2. Two point charges, +25nC and -75nC, are 10cm apart. Determine the force of attraction between them.

3. Determine the force of attraction of two negatively charge particle to the positively charge particle. Determine total force.

+12uC

-20uC-20uC

4cm

3cm

4. Find the total force develop by three positive charge to the negative charge particle in the figure

-20uC +10uC

+20uC+40uC

12in

10in

Semiconductor Materials• Semiconductors conduct less than metal

conductors but more than insulators.• Some common semiconductor materials

are silicon (Si), germanium (Ge), and carbon (C).

• Silicon is the most widely used semiconductor material in the electronics industry.

• Almost all diodes, transistors, and ICs manufactured today are made from silicon.

• Intrinsic semiconductors are semiconductors in their purest form.

• Extrinsic semiconductors are semiconductors with other atoms mixed in.

• These other atoms are called impurity atoms.

• The process of adding impurity atoms is called doping.

The figure below illustrates a bonding diagram of a silicon crystal.

• Thermal energy is the main cause for the creation of an electron-hole pair, as shown in Figure

• As temperature increases, more thermally generated electron-hole pairs are created.

• In the figure, the hole acts like a positive charge because it attracts a free electron passing through the crystal.

• The figure shows the doping of a silicon crystal with a pentavalent impurity.(N type)

• Arsenic (As) is shown in this figure, but other pentavalent impurities such as antimony (Sb) or phosphorous (P) could also be used.

• The figure shows the doping of a silicon crystal with a trivalent impurity.(P type)

• Aluminum (Al) is shown in this figure, but other trivalent impurities such as boron (B) or gallium (Ga) could also be used.

• A popular semiconductor device called a diode is made by joining p- and n-type semiconductor materials, as shown in Fig. a.

• The doped regions meet to form a p-n junction.

• Diodes are unidirectional devices that allow current to flow in one direction.

• The schematic symbol for a diode is shown in Fig. b.

The PN junction

Biasing of Diodes

1. Forward bias

2. Reverse bias

Diode Approximations

1. First approximation(switch)

2. Second approximation(voltage Ge=0.3V, Si=0.7V)

3. Third approximation(with internal resistance called bulk resistance)

Polarity of Diodes

Diodes

Cathode Lead

Anode Lead

Diodes

Cathode LeadCathode Lead

Anode LeadAnode Lead

Diode ApplicationDetermine whether the diode is forward or reverse

bias.

1.

V1 5D1 1N1183

R1 1k

Si

10V1K

I

2. V2 5

D2 1N1183

R2 1

k

Si

1K10V

I

3. Find the current and the voltage across the load if possible.

D3 1N1183D4 1N1183V3 5

R3

1k

Si Ge

12V1.5K

4.

D3 1N1183V3 5

R3 1

kD4 1N1183

Si Ge

12V1.5K

Si Si

5. Find the voltage and current in 1KΩ

V4 5

D5 1N1183 R4 1k

Ge

1K10V

6.Determine the current and voltage across 1.5KΩ

V5 5D6 1N1183 D7 1N1183

D8 1N1183 R5 1k

Si

Si

Si

1.5K12V

7. Determine which switch will turn “ON” the LED.(all diode are silicon)

V1 5D1 1N1183

D2 1N1183

D3 1N1183

D4 1N1183

D5 1N1183

LED1

CQX

35A

SW1

SW2

SW3

SW4

SW5

12V

8. Find the output voltage

D6 1

N118

3

R1 1

k

D7 1N1183

V2 5

12V

Si

Si

0.9K

Vo

9. Find the total current and output voltage

V1 5

D1 1N1183

D2 1N1183

D3 1N1183

D4

1N11

83

D5

1N11

83

R1

1k

15V

Si

Si

Si Ge

Ge

5

Vo

IT

Assignment no. 7

1. Determine whether the diode is in forward or reverse bias. Why?

V3 5D8 1N1183R2 1k R3

1k

Ge

2. Identify the switches that will make the LED to “ON”

D9 1N1183D10 1N1183D11 1N1183D12 1N1183

D13

1N

1183

D14

1N

1183

LED

2 C

QX

35A

V4 5SW6SW7SW8

SW9

SW10

SW

11S

W12

A

B

C

D

E F G

3. Find the output voltage Vo

D15 1N1183D16 1N1183

D17

1N

1183

V5 5

V6 5

6.8V

Si Si

Si

1.4V

Vo

4. Find the current and voltage across 2KΩ

V7 5

R4 1k

D18

1N

1183

V8 5

R5

1k

15V

2K

3V

0.5K

Si

Transistor- a three terminal device used for signal amplification.

Three parts: collector, base and emitter

Two types: bipolar junction transistor

field effect transistor

Types of transistor: pnp and npn

Symbol:

NPN PNP

T1 !NPNT2 !PNP

Construction:

nn p

p n p

e

b

c

e

b

c

npn transistor

pnp transistor

Diode equivalent

D1 1N11

83D2 1

N1183

N

P

N

D1 1N118

3D2 1

N1183

P

N

P

Transistor configuration:

Common base

Common collector

Common emitter

Current consideration: Ic + Ib = Ie

Transistor parameters:

The alpha, α, the ratio between the collector current and the emitter current’

The beta, β, the ratio between the collector current and the base current.

α = Ic / Ie, less than 1

β = Ic / Ib, greater than 1 usually 50 to 500.

Examplescomplete the table below

Ic Ie Ib α β

28.2828mA 0.9915

30.244mA 30.303mA

42.555µA 121

52.256mA 60.546µA

LOGIC GATES AND DIGITAL CIRCUITS

There are generally two types of digital logic: combinational and sequential.

Combinational logic refers to the type of logic that depends only in existing conditions to produce the outputs. This type of logic can be implemented using logic gates only.

Sequential logic refers to operations that need some form of memory device such as flip flops since the output depend not only on the current existing input conditions but to previous input as well

The Logic Gates

They are the basic building blocks in digital electronics. They are intended to implement different logic functions such as the NOT, OR, NOR, AND, NAND, XOR and XNOR. The logic gate, regardless of the technology used such as CMOS(complementary metal-oxide semiconductor) or TTL(transistor-transistor logic), is internally composed of an electronic circuit usually transistor based to provide a preset logic function.

There are many ways of describing the function of logic gates and other logic devices. The two most common are truth table and timing diagrams. A truth table is a tabulated list of all possible input and out combinations of a logic device. A timing diagram is a graphical method of showing the exact output behavior of a logic circuit for every possible set of input condition.

For a 2 input device, there are 4 possible combinations of inputs and output. The inputs can either be 0, 1 or even don’t care condition. The don’t care status means that the particular input has no effect on the output. This is usually marked by a D or an “x” symbol in many diagrams.

Truth table and Timing Diagram

truth tableinput outputA B X0 0 00 1 11 0 01 1 1

A

B

X

The InverterThe inverter is one of the most popular logic

gates in terms of use. It has one input and one output. This gate’s basic function is simply to complement the logic signal at its input. This means that is the input is 1, then the output is 0, and vice versa.

U1 SN7407

U2 SN7404

non inverting buffer

inverting buffer

Inverter (NOT gate)

A

A'

OR GateThe function of the OR gate is to provide a

high or 1 output when at least one of its input is 1. the output is low or 0 when all its inputs are 0. the OR gate may have two or more inputs

A

B

X

AND GateThe AND gate is a basic logic gate whose

output is a high logic output only when all input are high or 1. The most common IC AND gate is the 2 input AND gate. AND gates with more than 2 inputs are also available

A

B

X

NOR Gate

This is derived from OR gate. It produces a high logic output when the inputs are all at logic low or 0 and a low logic output when at least one input is at high or 1. This gate is formed by an OR Gate and followed by an inverter.

A

B

X

NAND Gate

The NAND Gate produces a low logic output only when all its inputs are high. This is simply a complement of the AND Gate. The NAND means NOT AND. This “only if” characteristics makes the NAND gate one of the most useful gates in logic design.

A

B

X

XOR Gate

Exclusive OR gate produces a high logic output only when one but all its input are high. When the inputs are all high or all low, the output is low. If there are odd number of 1, the output is 1.

A

B

X

XNOR Gate• This is the complement of XOR Gate. It

produces a logic low output only when one but not all its input are high. This gate is sometimes referred to as the equality gate because both its input must be the same to get a high output

A

B

X

Internal Diagram of an IC

Exercises Construct the truth table and the timing

diagram of the given logic gates

U3 SN7432U5 SN7432

U4 SN7404

AB

C

X

U6 SN7408U7 SN7408

U9 SN7432AB

CD

X

U1 SN7404

U2 SN7404U3 SN7404

U4 SN7408 U5 SN7432U6 SN7432

A

B

C

Find the possible output for S and Cout

5. Obtain the output function of the given logic gates using truth table and draw the timing diagram

U1 SN7408

U2 SN7408

U3 SN7432U4 SN7432

U5 SN7408

TP1TP2

TP3

TP4

X

AB

CD

Design a logic circuit that would generate the given function.

1. f(a,b,c) = a’b + c(ab+b’)

2. f(a,b,c) = a[b’c’ + ab]’ + ac’

3. f(a,b,c) = a + bc + b(a’bc’)

Assignment No. 8Design the given function using logic gates

and construct the truth table and timing diagram.

1. X = abd’ + d(a + bc’)

2. Y = bd’ + (a + b + c’)(a’ + b’ + cd)

3. f(a,b,c,d) = (ab + cd)(a’b + ab’)

4. X = abc’ + bcd’ + cd[ab’ + a’b]’

5. Y = (abcd’)’(ab + bc + cd’)

Problem Solving1. Design a logic circuit with 3 input such

that the output is a logic 1 when 2 or more of the inputs are high.

2. Design a logic circuit with 3 input such that the output will be high if two adjacent input are high.

3. Design a logic circuit with 3 input such that the output will be low if the decimal equivalent of the input are 2<decimal≤6

4. In a simple copy machine, a stop signal, S, is to be generated to stop the machine operation and energize an indicator light whenever either of the following conditions exist: (1) there is no paper in the paper feeder tray; (2) the two micro switches in the paper path are activated, indicating a jam in the paper path. The presence of paper in the feeder tray is indicated by a HIGH at the logic signal P. Each of the microswitches produces a logic signal (Q and R) that goes HIGH whenever paper is passing over the switch to activate it. Design the logic circuit to produce a HIGH at output signal S for the stated conditions.

5. A man decided to go out and have some relaxation period either Saturday or Sunday if his girlfriend is available. Design a circuit that would trigger his time of going out.

Flip-Flops and DecodersOne of the most basic memory elements is

the flip-flops. It is a bistable multivibrator whose output toggles back and forth between two stable states: 1 or high and 0 or low. The flip-flop is considered a memory element because it can store or hold a logic signal for as long as required conditions are met. Understanding them is essential in learning the operation of sequential logic circuits.

Multivibrator- a device that perform and generate pulses.

Astable MV- have no stable state. Their outputs continuously toggle between high and low levels. (oscillators)

Monostable MV- they are one shot circuits. They have one stable output state, either high or low. (pulsator)

Bistable MV- they are know as flip-flops. These devices are the basic counting and memory units in digital circuits. They have two stable states.

Set-Reset FF(SRFF NOR)It is commonly known as SRFF. The two

output states are meant to be complementary. The term SET and RESET may be thought of as ‘set to 1’ or ‘reset to 0’. The SRFF circuit shown is constructed using NOR gates. Notice that the configuration is actually symmetrical. The input labels may be interchanged as long as the output labels are also interchanged.

U3 SN7402U4 SN7402

TP1

TP2

TP3

TP4

S

R

Q'

Q

1

2

OperationInitially, assume the S input to be 1 and the R

input to be 0. if the S input is 1, then the Q’ will be 0 and the complement of Q output is 1. the important point is when the S input is 1, Q is also 1. now if the S input is 0 and R is 1, then the Q is 0 and the complement Q’ is 1. therefore when R pin is 1, then Q is 0.

if both inputs are 0, will Q and Q’ be 0? No. in this case, the previous condition has an effect. It will remain unchanged(hold)

S R Q Q’ OPERATION

0 0 H H no change

0 1 0 1 reset condition

1 0 1 0 set condition

1 1 x x unused(not applicable)

Timing Diagram

S

R

Q

0

1

1

0

0

0

0

1

0

0

SRFF (NAND)

TP1

TP2

TP3

TP4

U3 SN7400

U4 SN7400S

R

1

2

Q

Q'

Operation If R = S = 1, this condition is the normal

resting state, and if has no effect on the output state. The Q and Q’ will remain in whatever state they were in prior to this input condition.

If S = 0 and R = 1. this will always cause Q = 1 state, where it will remain even after SET returns to 1. this is called setting the latch(SRFF).

If S = 1 and R = 0, this will always produce Q = 0 state, where the output will remain even after RESET returns to 1. This is called clearing or resetting the latch.

If S = R = 0, this is not applicable.

S R Q Q’ condition

1 1 H H no change (hold)

0 1 1 0 resetting condition

1 0 0 1 setting condition

0 0 x x invalid

Timing Diagram

S

R

Q

0

1

1

0

0

1

1

1

1

1

CLK SRFFBoth the SRFF(NOR) and SRFF(NAND) is

disabled meaning there will be no change in the previous state if the CLOCK(CLK) is 0.

0

1

1

0 0

0

1

01

1

1

1

S

R

CLK

Q

1

1

1 0 1 1 00 1

Symbols of SRFF

S

R

Q

U6 Noname

S

R

Q

CLK SRFF SRFF

Delay Flip-Flops(DFF)The SRFF, although quite useful as memory

device has one disadvantage: S=R=1(NOR) and S=R=0(NAND) are never used. In digital circuits, this condition may easily be avoided by using a simple inverter.

S

R

Q

U6 Noname

U8 SN7404

TP5TP6

D

CLK

D

CLK

Q

Truth Table and Timing Diagram

00 1

0

1 1

1 10 1

D CLK Q CONDITION0 0 H no change (HOLD)1 0 H no change (HOLD)0 1 0 reset condition1 0 1 set condition

D

CLK

Q

JKFFAnother way of going around the

indeterminate condition of SRFF is to add AND gates to the input as shown.

TP1

TP2

U3 SN7400

U4 SN7400

U10 SN7400

U11 SN7400

U12 SN7408 U13 SN7408TP3

TP4

TP7Q

Q'

J

CLK

K

Symbol of JKFF

CLK

Q

Q'

J

K

CLK JKFF

Truth table for JKFF J K Q condition

0 0 H no change ( hold)

0 1 0 reset condition

1 0 1 set condition

1 1 T toggle (change 0 if previous is 1)

(change 1 if previous is 0)

If clock is present, there will be no change in condition as in the prior condition if it is disabled or 0.

Timing Diagram

J

K

CLK

Q

1 1 0 0 1 1 1

0 1 0 1 1 1 0

0

1

0 1 0 1 0 1

0

11

0

1

Draw the timing diagram of the given digital circuits

S

R

Q

U1 Noname

DE

Q

U2 SN74100TP1

TP2

TP3

1001001

0101010

0010110NOR

1. The simple circuit below uses NOR SRFF and DFF with clock

2. Construct the complete truth table and draw the timing diagram of the circuit below. The preset pin is disabled. U4 SN7432

U5 SN7404

J

K Q

QP

U6 SN74LS113

S

R

Q

U7 Noname

U8 SN7404TP6TP7TP8

AB

C

X

3. Find the output of the given circuit.

S

R

Q U10 Noname

DE

Q

U11 SN74100

U13 SN7432TP7

TP8TP9

TP10

NOR

110011

001100

111001

010101

4. Given the circuit below, the feedback loop is delayed for t sec, find the output.

J

K Q

QP

U1 SN74LS113

J

K Q

QP

U2 SN74LS113

D

C Q

QP

U3 SN7474TP1TP2

TP3TP4

TP5

U9 SN7404

001111

011111

100111

010101

X