Lecture 1 Admin and Intro

8/3/2019 Lecture 1 Admin and Intro

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Lecture #0

Administrative Topics

Dr. Riza MuhidaDepartment of Mechatronics EngineeringInternational Islamic University Malaysia


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Outlines

Teaching Team

Lecture Hours

Textbook

Tentative Course Outline Learning Outcome

Schedule


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Lecturer

Teaching Team

Dr. Riza MuhidaPhone : 0361964487

E-mail : [email protected]

Department of Mechatronics EngineeringInternational Islamic University Malaysia


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Required Textbook

Tony R. Kuphaldt (2004), Lessons In Electric Circuits, 1st Ed., Open Source Book.


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Tentative Course Outline

1. Introduction to Electric and Electronics

2. Ohm Principle, power and Energy

3. Introduction to Semiconductor4. Diode and the Applications

5. Transistor and Applications

6. Introduction to Digital Electronics, Numbering systemand Code, Basic Logic Gate and Boolean Algebra.

7. Combined logics, Sequential Circuit, Memory Device

8. Introduction to microprocessor and microcomputers

9. Microprocessor structural Design

10. Revision

KMEM 4110 Electronic and Microprocessor


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Course Objectives

The aim of this course is to acquaint the

students with the basic electric andelectronic components, quantity andunit, introduction to electronics, digital.Introduction to microprocessors and

microcomputers


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Quiz 15 %

Assignment 5%Mid Exam 20 %End Examination 60 %Total 100 %

Evaluation Method


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Lecture #1

Introduction to Electronics

Dr. Riza MuhidaDepartment of Mechatronics EngineeringInternational Islamic University Malaysia


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Basic Concept

Atoms and Electrical Charge

Figure 1 Model ofan Atom

Atoms are the building blocks of all matter.They are made up of protons, neutrons, andelectrons.

Every electron has a small negative (-) charge.

The proton has the same amount of charge exceptthat it is the opposite, positive (+) charge.

Neutrons are electrically neutral and have nocharge.

The protons and neutrons are located in the center

of atoms forming what is called the nucleus and theelectrons revolve around them.


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Figure 2 Interaction betweenelectrons and protons

Interaction between electrons and protons

It is very important to know that particles of like charges will repel andunlike charges will attract.

For example, two protons or two electrons will repel each other.

However, a proton and a electron will attract.

That is how the electrons are held inside the atom.

The attraction between the electrons and protons keeps the electronsin orbit much like the gravitational attraction between the sun and itsplanets.


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Current and ampere

Electric current is the amount of electrons, or charge, moving past a pointevery second. It is basically the speed of electron flow. The faster theelectrons flow, the higher the current.

Current is represented by the letter I. The basic unit for measuring current isampere. Ampere can be abbreviated to amp or just A.

1 amp = 1 coulomb/sec

Meaning for every amp, there are 6.25x10^18 electrons moving past a pointevery second.


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Potential difference and voltage

Figure 4. Analogy electron with amarble

To make sense of voltage, we will need to make an analogy.

Lets imagine that electrons are represented by a marble on a flat plane. Atthis point, the plane is level and the marble does not move. If the plane islifted at one side, the marble will roll down to the lower point.

In electricity, the high point is a point with lots of electrons and the low

point is a point with a lack of electrons. The high point is called the highpotential and the low point is the low potential. The difference betweenthese two points is called the potential difference. The larger the potentialdifference, the larger the voltage.

Figure 5. Energy potential


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Voltage can be thought of as the measure of the pressurepushing theelectrons. The higher the pressure, the higher the voltage.

Voltage is represented by the letter E. The basic unit of measure is volts or the

letter V. One volt will push 1 amp of current through 1 ohm of resistance.Resistance will be discussed in a later section.


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Power

Power is simply the amount of energy used or the amount of "work" acircuit is doing.

Power is represented by the letter P. The basic unit for measuring poweris watts or the letter W. To find power, all you need is a simple equation:

P=EI

or Power equals voltage times current.

For example, ifE = 9VI = 0.5AthenP = 9 * 0.5

P = 4.5W


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Resistance

When an electron is knocked out of an atom, it will fly off and hit another atom.If the electron strikes the atom with enough force, it will knock off another

electron. The atom that was just knocked off will hit another atom and so forth.Note that every time an electron strikes another, it is transferring its energy.Some of the energy is converted into heat every time it is transferred. Thevoltage will drop as the energy is transferred over long distances. Thus a longwire has a higher resistance than a short wire.

Some materials - such as copper and silver - does not hold on to its electronsvery tightly. Therefore it doesn't require much energy to knock off an electron.These materials are called conductors and has a very low resistance toelectron flow.

Materials such as clay and plastics hold on to their electrons more tightly thanconductors. It takes more energy to knock off an electron from these materials.These materials are called insulators and has a high resistance to electron flow.

Resistance is represented by the letter R. The basic unit of measure is ohm or the symbol (Greek omega).


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Ohm's Law- The relationship between Current, Voltage, andResistance.

The German physicist, George Simon Ohm, established that voltage involt, electrical resistance in ohms, and ampereres flowing through anycircuit are all related. Ohmss law states:It requires 1 volt to push 1 ampere through 1 ohm of resistance.Ohm law camn also be sated as asimple formula to calculate one value

of an electrical circuit if the other two are known.I=E/RWhere:I= Current in ampere (A)E= Voltage in volt (V)R= Resistance in ohms ()


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SI UNITS

The system of units used inTechnology and Science is the

Systeme Internationale dunites(International system of units).Usually abbreviated to SI units andis based on the metric system. Thiswas introduced in 1960 and is nowadopted by the majority of countries

as the official system ofmeasurement. The basic units inthe SI system are listed in the tableto the right with their symbols.


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Schematic Diagram

A schematic diagram shows how each component connect with another. It isa simple and easy to read outline of the circuit. Each type of component has

a unique symbol and a name (usually 1-2 letters).

Figure 2-1 A simple schematicdiagram

As you can see, this diagram has 3 components: the thing with 4 horizontallines, the triangle in a circle, and the thing with the wavy lines. Can you guesswhich is the battery? Yes, the 4 horizontal lines. The triangle in the circle

represents the light emitting diode and the wavy lines represent the resistor --both of which will be discussed in the components section. Note the "R1" nextto the resistor symbol and "R1 470 ohm" below the diagram. This tells youwhat value to use for that component. If there was a second resistor, thesecond resistor will be called R2.


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SIMPLE CIRCUIT

If the battery is 9 volts, what role has the resistor?


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COMPONENT AND CIRCUIT DETAILS

BATTERIES

Batteriescome in all shapes and

sizes. They store electrical chargeand as we all know when they are putinto an electronic device such as aportable radio, they provide thepower. The usual battery sizes areseen opposite.

Typical Battery Symbols


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LEDs

Light Emitting Diodes(LED) are very rugged, they last a very long time and theyare an optical source. (A LIGHT SOURCE)LEDs produce red, green, yellow, or orange light. They are used in a range ofproducts. Can you name any ?Infrared LEDs are also available although light from this type cannot be seen by

the human eye. These are used in security devices.LEDs are part of the diode family, consequently they must be connected the rightway round or current will not pass through. They are usually protected by aresistor. Resistors are used in circuits because LEDs can be destroyed byvoltages over 3 volts.


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SWITCHES

Typical Switch Symbols

KEYSWITCH

PUSH SWITCH ROCKERSWITCH

This switch is available

in different forms. Theyprovide limited securityas a key is required toswitch them on and

off.

These can be push to

make (push the switch

to allow the circuit towork) or push to break(push the switch to turnoff the circuit).

This switch is common

on many electricaldevices. For examplethey are found oncomputer units for

turning them on and off.


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TOGGLESWITCH

SLIDESWITCH

REED /MAGNETIC

SWITCH

These are available inminiature andstandard sizes. Theadvantage of thetoggle switch is that

they can be extendedand operated by alever.

Can be stiff tooperate and doesnot operatesmoothly.Available in a

range of sizes.

This is a thin glass tube thatcontains two thin strips ofmetal (the reeds). When amagnet is brought close tothe glass tube, the reedsmove together and makecontact and the switch isturned on. The reeds openagain when the magnet isremoved. Reed switches arecommon in alarm systems


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MICRO-SWITCH

TILT SWITCH PRESSURE PAD/ SWITCH

Micro-switches can

be very small.Usually they includea small arm whichwhen pressedclicks. They are veryuseful and can be

found on manymachines - used asafety switches.

One of the mostcommon types of tiltswitch uses a blob of

mercury in a small tube.

When the tube is tiltedthe mercury runs downand forms a bridgeacross the two contactsturning the switch on.

This is a soft flexible

switch available inmany sizes. It consistsof two flexibleconductive foil sheetsseparated by a thinfelt, paper or foam

layer. If pressure isapplied the conductivesurfaces touch and theswitch is on


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INCANDESCENT LAMPS (BULBS)


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Series Circuit

This is a called a series circuit. Current flows through each of thebulbs in sequence. Current flows through bulb A, then bulb B andfinally bulb C. The more bulbs that are added, the less bright theyshine. It is possible to added so many bulbs that they do not light atall. This is due to the resistance in each bulb.


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PARALLEL CIRCUITS

This is a parallel circuit. Current can flow through each of the bulbswithout first having to flow through any others.


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A SERIES / PARALLEL CIRCUIT

The circuit above is both series and parallel. If you look closely youwill see that the two bulbs are in series with each other whilst themotors are an parallel. All the components provide a clear path forthe current.


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THE DIODE

A diode allows electricity to flow in one direction only and blocks the flow inthe opposite direction. They may be regarded as one-way valves and they

are used in various circuits, usually as a form of protection.

Generally, diodes do not conduct until the voltage reaches approximately .6volts, this is called the threshold point. If the current becomes too high the

diode may crack or melt.

ZENER DIODES

Normally a current does not flow through a diode in the reverse direction.The Zener Diode is specifically designed to begin conducting in the oppositedirection when the reverse voltage reaches a voltage threshold. Zener diodesare sometimes used as a voltage sensitive switch.


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TYPICAL USES OF DIODES

REVERSE POLARITYPROTECTOR

TRANSIENT PROTECTOR

The diode in this circuit protects a radio or a

recorder etc... In the event that the battery orpower source is connected the wrong way round,the diode does not allow current to flow.Electronic devices can be damaged or evendestroyed if the polarity is reversed (positive andnegative are connected to the wrong terminals).

When an inductor device such as a relay is turned

off a high voltage can be generated for a short time(Dia 1). This voltage spike can damage the relay

and other components. However, the diode doesnot allow current to pass through it in the wrongdirection and short circuits this spike.The diode can also be used to protect a meter

from a reverse current (Dia 2).


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CAPACITORS (A mini rechargeable battery )

Capacitors are components that are used to store an electrical charge and areused in timer circuits. A capacitor may be used with a resistor to produce atimer. Sometimes capacitors are used to smooth a current in a circuit as theycan prevent false triggering of other components such as relays.

A capacitor is composed of two conductors separated by an insulating material

called a DIELECTRIC. The dielectric can be paper, plastic film, ceramic, air or avacuum. The plates can be aluminium discs, aluminium foil or a thin film ofmetal applied to opposite sides of a solid dielectric. The CONDUCTOR -DIELECTRIC - CONDUCTOR sandwich can be rolled into a cylinder or left flat


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HOW A CAPACITOR WORKS

When the circuit is switched on, the lightdependent resistor emits light and the capacitor

charges up. When the switch is turned off theLED stills emits a light for a few seconds becausethe electricity stored in the capacitor is slowlydischarged. When it has fully discharged it'selectricity the LED no longer emits light. If aresistor is introduced to the circuit the capacitor

charges up more slowly but also discharges moreslowly. What will happen to the light ?

Electrolyticcapacitors are polarisedwhichmeans they have a positive and negative leadand must be positioned in a circuit the rightway round (the positive lead must go to thepositive side of the circuit).They also have a much higher capacitancethan non-electrolytic capacitors


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UNIT OF CAPACITOR

Capacitors can be charged and discharged. The amount of charge that acapacitor can hold is measured in Farads or the letter F. However, 1F is too

large for capacitors, so microfarads(F) and picofarads(pF) are used. micro= 1/1,000,000 and pico = 1/1,000,000,000,000

So 100,000pF = 0.1F = 0.0000001F

DC current cannot flow through a capacitor since the dielectric forms an opencircuit. Capacitors come in all shapes and sizes and are usually marked withtheir value.

Some values are marked in picofarads using three digit numbers. The firsttwo digits are the base number and the third digit is a multiplier.For example, 102 is 1000 pF and 104 is 100,000 pF = 100 nF = 0.1 uF. .


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Ceramic capacitors are brown and has a discshape. These capacitors are non-polarized, meaning

that you can connect them in any way. To find thevalue, you simply decode the 3 digit number on thesurface of the capacitor. The coding is just like theresistor color codes except that they used numbersinstead of colors. The first 2 digit are the significantfigures and the third digit is the multiplier. Thesecapacitors are measured in pF.

Electrolytic Capacitors has a cylinder shape.These capacitors are polarized so you mustconnect the negative side in the right place. The

value of the resistor as well as the negative side isclearly printed on the capacitor. These capacitorsare measured in F.

We will only be discussing two types of the most commonly used capacitors:Ceramic and Electrolytic.


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RESISTORS

Resistors determine the flow of current in an electrical circuit. Where there is highresistance then the flow of current is small, where the resistance is low the flow of

current is large. Resistance, voltage and current are connected in an electricalcircuit by Ohms Law.

Resistors are used for regulating current and they resist the current flow and theextent to which they do this is measured in ohms (). Resistors are found inalmost every electronic circuit.

The most common type of resistor consists of a small ceramic (clay) tubecovered partially by a conducting carbon film. The composition of the carbondetermines how much current can pass through.


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Resistors are too small to have numbers printed on them and so they aremarked with a number of coloured bands. Each colour stands for anumber. Three colour bands shows the resistors value in ohms and thefourth shows tolerance. Resistors can never be made to a precise value

and the tolerance band (the fourth band) tells us, using a percentage, howclose the resistor is to its coded value. The resistor on the left is 4700ohms.

47R means 47 ohms5R6 means 5.6 ohms6k8 means 6800 ohms

1M2 means 1 200 000ohms

A common value is 'K'which means onethousand ohms.


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RESISTORS

The color bands around the resistors are color codes that tell you its resistancevalue. Recall that resistance is measured in ohms.

The tolerance bands indicates the accuracy of the values. A5% tolerance (gold band) for example, indicates that theresistor will be within 5% of its value. For most applications,a resistor within 5% tolerance should be sufficient.

To get the value of a resistor, hold the resistor so that thetolerance band is on the right.

The first two color bands from the left are the significantfigures - simply write down the numbers represented by thecolors. The third band is the multiplier - it tells you how many

zeros to put after the significant figures. Put them alltogether and you have the value.


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RESISTORS IN SERIES AND INPARALLEL

Resistors in SERIES - When resistorsare connected in series, their values areadded together: R total=R1+R2

Resistors in PARALLEL -When

resistors are connected in parallel, theirtotal resistance is given as:

1/Rtotal = 1/R1 + 1/R2

VARIABLE RESISTORS

Variable resistors have adjustablevalues. Adjustment is normallymade by turning a spindle (e.g.the volume control on a radio) ormoving a slider.


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THE RELATIONSHIP BETWEEN CAPACITORSAND RESISTORS

A simple circuit is shown shows four capacitors and resistors in parallel. Onthe left hand side of the circuit an LED is seen, this is protected by a 300 ohm

resistor. As the switch is closed the capacitors can be seen to charge up andthe LED lights immediately. When the switch is opened the LED stays on for ashort time and then fades slowly. This happens because the each capacitorhas a charge of electricity. This is released slowly when the +9 volts is

switched off.

The total capacitance iscalculated by simply addingthe values of the capacitorstogether


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LIGHT DEPENDENT RESISTORS

LDRs or Light Dependent Resistors are very useful especially in light/darksensor circuits. Normally the resistance of an LDR is very high, sometimesas high as 1000 000 ohms, but when they are illuminated with lightresistance drops dramatically.

When the light level is low the resistance of the LDR is high. This preventscurrent from flowing to the base of the transistors. Consequently the LEDdoes not light.


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THE PRESET RESISTOR

Preset resistors are used incircuits when it is necessary to

alter the resistance. Dark/lightand temperature sensors usuallyhave these components as thepreset resistor allows the circuitto be made more or lesssensitive (they can be turned up

or down - reducing or increasingresistance).


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The two circuits below are sensor circuits. The one of the left is a temperaturesensor and the one on the right is a light sensitive circuit. Increasing the value ofthe preset resistor by turning the centre with a small screwdriver makes the circuitless sensitive. For instance, the temperature sensor would require a higher

temperature and the light sensitive circuit would need more intense light beforethey activated.


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THE THERMISTOR

An example of a thermistor is seen to the left. They aremade up of a mixture of sulphides or oxides or

sometimes metals such as copper, iron or cobalt. Theytend to be formed into a disc or a bead sealed withplastic or glass.

They have great resistance at low temperatures butwhen they warm up their resistance decreases rapidly.

Current can then flow through them. This makes themideal as one of the components for a temperaturesensor.


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Build the simple thermistor circuit below. When the thermistor is cool or coldthe LED should not light because of the high resistance.

Circuit explanation in detail:

When the thermistor is warmed up by the hairdrier its resistance drops, this will take a fewseconds. As its resistance drops current beginsto flow from positive 9 volts to negative 0 volts.Current flows into the base of the transistors

allowing the LED to light.The preset resistor can be turned up or down toincrease or decrease resistance, in this way itcan make the circuit more or less sensitive.

1. Explain how this circuit could be used in the home.

2. What is the role of the preset resistor ?


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POTENTIAL DIVIDERS

What are they - they can be used to split the voltageof a circuit. They are widely used in electronic circuits

for setting and adjusting voltages - e.g. in radios,games and toys. You may find that you need a supplyof 6 volts and you have a 9 volt battery, your onlyoption may be to make a potential divider.

If the resistor values are changed to 2K and 1K the

voltage will be 6v. The voltage at the centre isdetermined by the ratio of the two resistor valuesand is given by the formula:

V = supply voltage x R2/R1+R2V= 9v x 2000

1000+2000v = 9v x (2000/3000 ohms)V = 9v x 0.6666666 ohmsV = 6v


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TRANSISTORS

Transistors can be regarded as a type of switch, as can many electroniccomponents. They are used in a variety of circuits and they are central toelectronics and there are two main types; NPN and PNP. Most circuits tend

to use NPN. There are hundreds of transistors which work at differentvoltages but all of them fall into these two categories.


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TRANSISTORS

Transistors are manufactured in different shapes but they have three leads(legs).

The BASE- which is the lead responsible for activating the transistor.The COLLECTOR- which is the positive lead.The EMITTER- which is the negative lead.The diagram below shows the symbol of an NPNtransistor. They are notalways set out as shown in the diagrams to the left and right, although thetab on the type shown to the left is usually next to the emitter

The leads on a transistor may not always be

in this arrangement. When buying a transistor,directions will normally state clearly which

lead is the BASE, EMITTER or COLLECTOR.


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SIMPLE USE OF A TRANSISTOR

Diagram 'A' shows an NPN transistor which is often used as a type of switch. A smallcurrent or voltage at the baseallows a larger voltage to flow through the other two leads(from the collectorto the emitter).

The circuit shown in diagram B is based on an NPN transistor. When the switch is presseda current passes through the resistor into the baseof the transistor. The transistor then

allows current to flow from the +9 volts to the 0vs, and the lamp comes on.

The transistor has to receive a voltage at its base and until this happens the lamp doesnot light.The resistor is present to protect the transistor as they can be damaged easily by too higha voltage / current. Transistors are an essential component in many circuits and are

sometimes used to amplify a signal.


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THE DARLINGTON PAIR

Transistors are an essential component in a sensor circuit. Usually transistors arearranged as a pair, known as a DARLINGTON PAIR. It is very important that you

can identify this arrangement of transistors and state clearly why they are used.A darlington pair is used to amplify weak signals so that they can be clearlydetected by another circuit or a computer/microprocessor.

A second transistor is added to the circuit, the circuit is now likely towork as the original signal / current is amplified.

TRANSISTOR FORMULAS


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TRANSISTOR FORMULAS

Transistors are used to amplify current and so in an examination you couldbe asked to find the BASE current or COLLECTOR current or the GAIN.The GAIN is simply the amount of amplification. The formulas and example

questions are set out below:


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1. If the collector current of a transistor is 0.12 amps and the gain is40, what is the base current?

2. If the collector current of a transistor is 0.4 amps and the basecurrent is 0.002 amps, what is the current gain?

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