Basic Electronics

Electricity

Is an invisible force which can produce: heat light sound motion

Electricity can be broken down into:

Electric Charge Voltage Current Resistance

Negative & Positive Charges

What do the effects of electricity in TV, radio, a battery, and lightening all have in common?

Basic particles of electric charge with opposite polarities.

Electrons

The smallest amount of electrical charge having the quality called negative polarity.

Electrons orbit the center of atoms.

Protons

The proton is a basic particle with positive polarity.

Protons are located in the nucleus of atoms along with neutrons, particles which have neutral polarity.

Electrically, all materials fall into 1 of 3 classifications:

Conductors Insulators Semi-Conductors

Conductors

Have 1 valence electron Materials in which electrons can move freely

from atom to atom are called conductors. In general all metals are good conductors. The purpose of conductors is to allow

electrical current to flow with minimum resistance.

Insulators Have 8 valence electrons Materials in which electrons tend to stay put and do

not flow easily from atom to atom are termed insulators.

Insulators are used to prevent the flow of electricity. Insulating materials such as glass, rubber, or plastic

are also called dielectrics, meaning they can store charges.

Dielectric materials are used in components like capacitors which must store electric charges.

Semi-Conductors Have 4 valence electrons Materials which are neither conductors nor

insulators Common semi conductor materials are carbon,

germanium and silicone. Used in components like transistors

The Symbol for Charge

The symbol for charge is Q which stands for quantity.

The practical unit of charge is called the coulomb (C).

One coulomb is equal to the amount of charge of 6.25X1018 electrons or protons stored in a dielectric.

Harnessing Electricity

First we must separate the + & - charges in matter.

Changing the balance of forces produces evidence of electricity.

Example: A battery. Its chemical energy separates electric charges to produce an excess of electrons on one lead, and an excess of protons on the other.

Voltage Potential refers to the the possibility of doing work. Any charge has the potential to do the work of

attracting a similar charge or repulsing an opposite charge.

The symbol for potential difference is E (for electromotive force)

The practical unit of potential difference is the volt (V)

1 volt is a measure of the amount of work required to move 1C of charge

Current When a charge is forced to move because of a

potential difference (voltage) current is produced.

In conductors - free electrons can be forced to move with relative ease, since they require little work to be moved.

So current is charge in motion. The more electrons in motion the greater the

current.

Amperes

Current indicates the intensity of the electricity in motion. The symbol for current is I (for intensity) and is measured in amperes.

The definition of current is: I = Q/T Where I is current in amperes, Q is charge in

coulombs, and T is time in seconds.

1 ampere = 1 coulomb per second

Resistance Opposition to the flow of current is termed

resistance. The fact that a wire can become hot from the

flow of current is evidence of resistance. Conductors have very little resistance. Insulators have large amounts of resistance.

Ohms

The practical unit of resistance is the ohm designated by the Greek letter omega: Ω

A resistor is an electronic component designed specifically to provide resistance.

Closed Circuits

In applications requiring the use of current, electrical components are arranged in the form of a circuit.

A circuit is defined as a path for current flow.

A Simple Circuit

Common Electronic Component Symbols

A Complex Audio Circuit

Open Circuits

The Circuit is a Load on the Voltage Source

The circuit is where the energy of the source (battery) is carried by means of the current through the the various components.

The battery is the source, since it provides the potential energy to be used.

The circuit components are the load resistance - they determines how much current the source will produce.

Direction of Electron Flow

The direction of electron flow in our circuit is from the negative side of the battery, through the load resistance, back to the positive side of the battery.

Inside the battery, electrons move to the negative terminal due to chemical action, maintaining the potential across the leads.

Electron Flow in a Simple Circuit

DC

Circuits that are powered by battery sources are termed direct current circuits.

This is because the battery maintains the same polarity of output voltage. The plus and minus sides remain constant.

Waveform of DC Voltage

Characteristics of DC

It is the flow of charges in just one direction and...

The fixed polarity of the applied voltage which are characteristics of DC circuits

AC An alternating voltage source periodically

alternates or reverses in polarity. The resulting current, therefore, periodically

reverses in direction. The power outlet in your home is 50 cycle ac -

meaning the voltage polarity and current direction go through 50 cycles of reversal per second.

All audio signals are AC also.

Waveform of AC Voltage

Complex Voltage

This is a more realistic view of what an audio signal’s voltage would look like

Comparison of DC & ACDC VoltageDC Voltage AC VoltageAC Voltage

Fixed polarityFixed polarity Reverses polarityReverses polarity

Can be steady or vary in Can be steady or vary in magnitudemagnitude

Varies in magnitude Varies in magnitude between reversals in between reversals in polaritypolarity

Steady value cannot be Steady value cannot be stepped up or down by a stepped up or down by a transformertransformer

Used for electrical power Used for electrical power distributiondistribution

Electrode voltage for tube Electrode voltage for tube and transistor ampsand transistor amps

I/O signal for tube and I/O signal for tube and transistor ampstransistor amps

Easier to measureEasier to measure Easier to amplifyEasier to amplify

Heating Effects the same for both AC and DC current

Many Circuits Include both AC & DC Voltages

DC circuits are usually simpler than AC circuits. However, the principles of DC circuits also

apply to AC circuits.

Impedance

Impedance is resistance to current flow in AC circuits and its symbol is .

Impedance is also measured in ohms.

Grounding In the wiring of practical circuits one side of the voltage

source is usually grounded for safety. For 120 V - ac power lines in homes this means one side of

the voltage source is connected to a metal cold water pipe. For electronic equipment, the ground just indicates a metal

chassis, which is used as a common return for connections to the source.

Common Symbols/ Names for Ground in Electric Circuits

Linear Proportion Between E and I for a Constant Resistance

OHM’s LAWOHM’s LAW

Ohm’s Law

The amount of current in a circuit is dependent on its resistance and the applied voltage. Specifically I = E/R

If you know any two of the factors E, I, and R you can calculate the third.

Current I = E/R Voltage E = IR Resistance R = E/I

Power The unit of electrical power is the watt. Power is how much work is done over time. One watt of power is equal to the work done in one

second by one volt moving one coulomb of charge. Since one coulomb a second is an ampere:

Power in watts = volts x amperes P = E x I

3 Power Formulas P = E x I P = I2 x R P = E2 / R

Conversion FactorsPrefixPrefix SymbolSymbol Relation to Relation to

basic unitbasic unitExamplesExamples

MegaMega MM 1,000,000 1,000,000 or 1x10or 1x1066

5MΩ =5MΩ =5x105x106 6 ΩΩ

KiloKilo kk 1,000 or1,000 or1x101x1033

18kV =18kV =18x1018x1033 V V

MilliMilli mm .001 or .001 or 1x101x10-3-3

48 mA = 48 mA = 48x1048x10-3-3AA

MicroMicro .000001 or.000001 or1x101x10-6-6

1515V =V =15x1015x10-6-6VV

Components and vocabulary

Battery: pushes on the electrical charges (though none will actually flow if the circuit

isn’t complete) – the battery has two terminals labeled positive (+) and negative (-)

– the most negative voltage region in the circuit, often the negative end of the battery, is sometimes called “ground” or 0 volts – the

amount of push the battery supplies is the “battery voltage”, often 1.5 V or 9 V or 12 V (with respect to ground) – as a battery gets worn out (or if it gets too cold!) its voltage

will go down until the battery is too weak to continue to push current through the circuit

symbol

Wire: provides a path through which electrical current can flow –

ideally a wire has no resistance

symbol

Resistor: serves as a current path but limits the amount of electrical current flow and reduces the pressure (i.e. drops the voltage) – resistance is measured in Ohms (Ω) – for resistors it doesn’t matter which way + and – are connected – when current flows through a resistor the resistor may get hot (i.e. it “dissipates” energy), so resistors can also be used as heaters

symbol

Switch: place where a current path can be mechanically opened and closed, to start or stop the flow of electrical current – switches are used to turn things ON and OFF – place the switch in series with the component(s) it is meant to control, like a battery symbol

Capacitor: serves as a place to temporarily store electrical charge, like a temporary battery – “charge it up” (store electrical charge) then “discharge it” (temporarily produce electrical current) – capacitance is measured in Farads (F) – electrolytic capacitors are ones in which it matters which way + and – are connected

symbol

Diode: serves as a one-way valve, only allowing current to flow one

direction under normal circumstances – an LED (light

emitting diode) is a diode (often red or green) that glows when current flows through it – diodes must be

inserted the right way around for the circuit to operate correctly

symbols

Voltage regulator: a chip that can be powered by a range of voltages but uses internal circuitry to drop the voltage to output a very stable voltage (e.g. a “5 V regulator” might be able to able to be

able to run off any voltage from 6 V up to 20 V, but it always outputs exactly 5 V) –

this is handy for providing a constant voltage to components even when dealing with batteries that can vary in voltage and circuits that can vary in overall resistance

IC (Integrated Circuit, AKA chip): a silicon chip with many tiny transistors

on-board which can be programmed to make decisions (a microprocessor chip), to store digital information (a memory chip), to convert digital input to analog form (DAC), or vise versa (ADC), etc. –

connects to other components through its multiple legs, called pins – be very

careful never to put a chip in backward!

ADC (Analog to Digital Converter): a chip that takes analog (continuous) voltage

input, perhaps from a sensor, and converts it to digital form for ease of use

Breadboard: a board into which components

can be plugged and unplugged, allowing one

to build and check circuits without having to be as permanent as

soldering them together

PCB (Printed Circuit Board): insulating board onto which

components can be soldered, with metallic traces etched into

the board to make electrical connections without having to

use external wires

Perf. Board (Perforated (Circuit) Board): insulating board onto

which components can be soldered, with no metallic traces etched between holes like on a PCB – using perf. board is more

permanent than using a breadboard but you need to connect components with

external wires

Transistor: 3-leg device used in logic circuits so that a small/weak electrical

current at one point can control a much larger/more-powerful electrical current

elsewhere in the circuit

Sensor: a device, often powered using +5 V and ground (+0 V) connections, that has a third

output the voltage of which varies predictably and reproducibly as

some physical parameter changes like temperature or air pressure – needs to be “calibrated” (i.e. the output needs to be checked using

known physical conditions) so output values can be correctly

interpreted

Socket: a dummy set of receptacles that matches the pins on a chip – the socket is soldered onto the board and the chip snaps into it so that

the chip can be replaced (carefully!) without

resoldering if it goes bad

Cable: a wire or set of parallel wires connecting

components together – for example, sensors often use a 3-wire cable with the wires

used for +5 V, ground (+0 V), and signal (output voltage)

Battery pack: a device for holding multiple (identical)

batteries, either in series (+ of one battery attached to the – of the next, in which case the total voltage is the sum of the battery

voltages) or in parallel (all + terminals connected together, all – terminals connected together, in which case the battery pack has the same voltage as each

individual battery, but it will last longer (i.e. can provide current for a longer amount of time))

Audio jack: used to make a pull-before-flight pin to start a flight computer just before we let go without having to open up a payload box

Male and female headers: used to allow quick

electrical connections between sensors, flight

computers, for programming, etc.

Shrink wrap: plastic insulation tubing one can slide over exposed metal,

like a solder joint, to insulate it electrically from

nearby wires – shrink wrap contracts (shrinks!) when heated with a heat gun – think ahead; you might need to put the

shrink wrap on before you do the soldering

Using a multimeterto make resistance andvoltage measurements

Multimeter: a device with two probes (red (positive) and black (negative)) with which one can make resistance,

voltage, and current measurements – for resistance and voltage measurements (all we’ll be doing in this class) always plug the black probe into the socket labeled “COM” and the

red probe into the socket labeled “V Ω mA”

Measuring resistance in Ohms (Ω). Turn the dial to a value on the Ohms scale larger than the resistance you expect. Touch the two probes to either end of the resistor (preferably when

it is not part of any circuit, lest there be alternate current paths around the resistor). Adjust the dial downwards as

necessary. Read the value of the resistance in Ohms, kiloOhms, or MegaOhms. (Note – you can also read off

resistance values by using resistor color codes.)

Measuring DC voltage (i.e. battery-type voltage). Turn the dial to a value on the DC Volts scale larger than the voltage you expect. Touch the two probes to the two points on the

circuit between which you want to know the voltage change, trying to put the black probe on the point with the lower

voltage (i.e. closer to “ground”). Adjust the dial downwards as necessary and read off the value in volts. Notice that the reading is the voltage drop from the red (positive) probe to the black (negative) probe, so a positive reading means that the red probe is indeed at a more positive voltage than the black probe. On the other hand, a negative reading means the red probe is more negative than the black probe. (See

next slide for photos of a voltage reading being made.)

Using a multimeter to measure the voltage of a battery. Notice that the red probe goes to the +

terminal and the black probe goes to the – terminal to get a positive value on the screen.

Circuit Protection

Circuit Protection

• Types of Fused Protection

How to pull them

Fuses• Auto-fuse

(blade type and Color coded)

• Mini-fuse • Maxi-fuse A. TEST HOLES

B. REMOVAL

Maxi-fuses• Combination blade / cartridge• Protects main circuits• Safer than fusible link• Cover fewer circuits than a fusible

link• Often in Power Distribution box

Ceramic and GlassCeramic and Glass

• Rated by current failure level• Three letter code for type and size• Glass style replaces ceramic• Caution in pulling

Two reasons for blowingWhere do they blow?

New Circuits

• What size of fuse should I install?

• Use Watts law. Watts divided by volts

?

FUSIBLE LINKS

• Lighter gauge wire than main conductor

• Covered with special insulation

• Protect Main circuits• Usually under hood

Fusible Links Repair• Location• Circuits protected• Insulation

– Visual checks • Installing a new link

– 4 wire sizes smaller (4 numbers larger)

– Soldering

Fuses

Male Pal fuses Female Pal fuses Bolt on Pal Fuses

Circuit Breaker• Why circuit breakers• Styles• Deterioration

TESTING CIRCUIT PROTECTION DEVICES

• Must inspect closely• Type of failure determines cause• Best to use DVOM• Do not overload circuit by installing to large of

fuse or tin foil• Connections must be tight• Do not use un-fused jumper wire

Electrical Components

Switches

• Controls electrical current (N.O. or N.C.)

• Single-pole, single throw (SPST)

• Momentary Switch• Single-pole, double

throw switch (SPDT)• Ganged Switch

Relays

• Electromagnetic Switches (Relays)

• Two Circuits– Control Circuit– Load Circuit

• Magnetic field operates contacts

• Late model relays are universal

TESTING RELAYS

• Can use several methods to test• Must Check both circuits• Be careful using test light if relay is operated

by computer• Can bench test if needed• Some relays have schematic on them• Must be correct resistance

SOLENOIDSSOLENOIDS• Electromagnetic

device with a iron core• Does mechanical work• Core is moveable and

does work• Can test with DVOM

• Usually used to control fan motor speeds

• Resistance is changed by control of switch

• Controls current to change speeds

• Thermal fuse

Variable Resisters

• Rheostats– Two terminals– Higher current

• Potentiometer– Three terminals– Lower current

• Many uses for variable types

The three types of circuit defects are:

• Shorts• Grounds• Opens

– poor connections

TESTING FOR CIRCUIT DEFECTS

• DVOM IS BEST TO USE!• Must know circuit operation before can

diagnose problem• Must know how to use equipment and which

equipment to use.

Now, did he say, Now, did he say, “Amps, Volts or “Amps, Volts or

Ohms”?Ohms”?

Electronic Components

ELECTRONIC COMPONENTS• Passive Components: resistance, capacitance inductanceActive Components:

Semiconductor Devices : Semiconductor diode, zener diode, and varactor diode etc.Uni-junction transistor, Bipolar junction transistor (BJT), FET, silicon, Controlledrectifier etc.Vacuum Tube Devices : Vacuum tube diode, triode, Tetrode, Pentode, Hexode,Heptode etc.Gas Tube Devices : Gas diodes, Thyratons etc.Photo Sensitivity Devices : Gas photodiodes, photo multiplier tubes, photodiodes,light emitting diode, photosensitive transistor etc.

What are resistors?

Resistors provide a specific amount of resistance to a path in a circuit or wire. Ohm's law is used to calculate the properties related to resistance.

Ohm's Law: I = V/RI = Current measured in AmpsV = Voltage measured in VoltsR = Resistance measured in Ohms

Resistors are color coded.

Resistor Color Code

Resistor Color Code Wheel Calculator

• Before testing a resistor, • first establish what an accurate reading for the

specific resistor should be. • Next, connect the multimeter leads to the specific

resistor and run a test. • If the results are too high,

• this may be indicative of an open resistor, or a resistor that has acquired a higher value.

• Other circuit components typically cause the reading to decrease, so a higher value should be interpreted as a possible sign of a problem.

Variable resistor: The potentiometer

Voltage dividersTry out the different pots.

THERMISTORS

• A Thermistor is non-linear resistance made of semiconductor material that is extremely sensitive to change in temperature.

• For a small change in body temperature of a Thermistor, there is an appreciable change in its resistance, whereas most conductors have a positive temperature coefficient, the thermistor can exhibits a positive or negative temperature coefficient, (NTC).

• The thermistor is mostly negative temperature coefficient resistances.

• The resistances of thermistor decreases rapidly for increased temperature.

VARISTORS

• These are voltage dependent resistances. • They also fall under the category of nonlinear• resistors. • According to the Ohm's Law the current is

directly proportional to the impressed voltage but in case of varistors the current is proportional to the nth power of the impressed voltage i.e.

I α Vn, where I is the current in Amperes and V is the impressed voltage on the Varistors.

CAPACITORS :CAPACITORS :• It stores the charge across its two plates. • Capacitor opposes the change of voltage across its plates; the electric field developed across

the plate opposes the rapid change in voltages. • It produces phase difference between voltage applied to it and the current, which passes

through it.• The current leads the voltage by 90° in the ideal capacitance with infinite resistance across

the plates. • Design of capacitor is connected with relation of the proper electric material for particular

type of application. • The dielectric material used for capacitors may be grouped in the various classes

What are capacitors?

Capacitor is two separated charges.Known charge up time.Know discharge time.Two major kinds• Electrolytic, asymmetric, bipolar • Ceramic, symmetric

• The behavior of capacitor at various frequencies may be grouped into the following seven classes.

• Mica, glass, air, and low loss ceramic capacitors are used from few kHz to few hundreds MHz.

• Paper and metalized paper capacitor cover the frequency range from few Hz to few hundred kHz.

• High dielectric constant ceramic capacitor can only be used between the frequency ranges from few kHz to few, hundred of kHz however, they can find use from very low frequency to 1000 kHz.

• Aluminum electrolytic capacitor can find use at power frequency from 10Hz to 1000Hz but can be used up to 10 kHz.

• Tantalum electrolytic capacitor may be used from dc to few hundred Hz.• Polyethylene, tere-phthalate (Mylar), cellulose acetate capacitor may find use from

few hundred Hz to few MHz.• Polystyrene, polyethylene, poly-tetra-fluoro-ethylene (Teflon) capacitors are used

from dc to 1000 MHz range. They are reported to give satisfactory performance even at higher frequencies.

• The capacitance units in farads, G F, pF, nF

CAPACITORS :CAPACITORS :

• To test a capacitor in a PCB, one end of the capacitor should be removed from the circuit.

• The power supply of DC voltage should match the range of the capacitor so as not to overload the device.

• When voltage is applied several outcomes are possible: • If the capacitor has shorted the meter will simply

reflect the output voltage of the power supply.• If the capacitor is leaking the meter reading will

jump high and then drop low again (but not all the way to zero).

• If the meter registers no jump at all, the capacitor is either open or capacitance is too low to register a result.

CAPACITORS :CAPACITORS :

Capacitors in seriesCapacitors in series

Capacitors in Parallel

They can provide energy, however briefly.They can smooth out a signal.

Attach the battery briefly to fill the capacitor.

Capacitors in series and parallel

Make a voltage regulator

INDUCTORSINDUCTORS• Like capacitors, inductors also store energy

in one part of AC cycle and return it during the next part of the cycle.

• Inductance is that property of a device that reacts against a change in current through the device.

• Inductors are components designed for use in circuits to resist changes in current and thus serve important control functions.

• Inductor designed is based on the principle that a varying magnetic field induces a voltage in any conductor in that field.

• Thus, a practical inductor may simply be a coil wire.

INDUCTORS• The current in each loop of the coil produces a magnetic field that passes

through neighboring loops. • If the current through the coil is constant the magnetic field is constant

and no action takes place. • A change in the current, however, produces a change in the magnetic field. • The energy absorbed or released from the changing magnetic field reacts

against the change in current, and this is exhibited as in induced voltage (electromotive force, emf), which is counter to the change in applied voltage.

• The inductor thus behaves as an impedance to ac current.• The counter emf is directly proportional to the rate of change of current

through the coil (VL=L[di/dt]). – The proportionality constant is the inductance L, which has the unit of henrys

(H) – In an ac circuit the inductor offers reactance to alternating current. – The inductive reactance XL has the units of ohms and is given by XL = wL = 2πfL

• Total inductance L = L1 + L2 + L3 -----------• Inductances in parallel : 1/L = 1/L1 + 1/L2 + 1/L3

SEMICONDUCTORS DEVICESSEMICONDUCTORS DEVICES• A semiconductor is a substance which has resistivity

(.0001 to 0.5 Ωm) in between conductors and insulators e.g. germanium, silicon, carbon etc.

• When a semiconductor is neither a good conductor nor an insulator, then why not to classify it as a resistance material?

PROPERTIES OF SEMICONDUCTORS• The resistivity of semiconductor is less than an insulator

but more than a conductor.• The semiconductors have negative temperature coefficient

of resistance i.e. the resistance of semiconductor decreases with the increase in temperature and vice versa.

• For example germanium is actually an insulator at low temperatures but it becomes a good conductor at high temperatures.

• When a suitable metallic impurity (e.g. arsenic, gallium etc.) is added to a semiconductor, its current conducting properties change appreciably. This property is most important.

SEMICONDUCTORS DEVICESSEMICONDUCTORS DEVICES

Two type of semiconductor material known as P - type and N - type such

as silicon and germanium.

• p-type : Impurity of lower group, it contain excess of holes or deficiency of electrons.

• n-type : impurity of higher group, contains excess of electrons or deficiency of holes.

SEMICONDUCTORS DEVICESSEMICONDUCTORS DEVICES

DIODES • By forming a junction of n & p type material. Barrier potential is

formed across the junction due to crossing of holes to n side and crossing of electron to p side.

• This property of current flow in only one direction i.e. when the diode is forward biased.

• Though, theoretically the forward resistance of the diode is zero but practically it is not. The voltage drop in forward direction is V = I * Rd.

CHARACTERISTICS • Where Rd is dynamic forward resistance.• The junction drop is 0.3V in Germanium and 0.7V in

silicon diode.

SEMICONDUCTORS DEVICESSEMICONDUCTORS DEVICES

Full Wave Bridge RectifierFull Wave Bridge Rectifier

ZENER DIODEThese diodes are operated in reverse bias mode, as the reverse bias is increased the resistance remains constant until a certain value known as avalanche point is reached due to avalanche effect the current suddenly increases and the voltage across it becomes almost constant.

VARACTORS (voltage variable capacitors)• When a p-n diode is reversed biased the depletion, region

becomes devoid of free electrons and holes.• Thus in such a situation the depletion layer may be considered to

be layer of dielectric while the p and n regions as the plates of capacitors.

• When the reversed biased increased the width of the depletion layer will increase, hence the capacitance will decrease.

• While with reduction of reverse bias the capacitance will increase • Such types of diodes are also known as voltage variable capacitors

or varactors.

Tunnel Diodes• Just like other general diodes, a

tunnel diode consists of a pn junction. But the depletion layer in it is extremely narrow. Even the fastest of silicon diode is no match against these diodes.

When a forward voltage is applied to a tunnel diode, a very narrow stream of electrons forces its way across and through the pn junction. This phenomenon is called "tunneling" and hence the name tunnel diode. This happens because the doping level used in it is extremely high. The electronic symbol used for a tunnel diode is shown in the adjacent figure.

Unique Property of Tunnel DiodesUnique Property of Tunnel DiodesIf we look at the graph, it indicates how a tunnel diode behaves when a forward voltage and current is applied to it. It is clearly evident that it has "negative resistance characteristics“.

After an initial peak, the forward current starts decreasing with an increase in the forward voltage up to a certain extent (indicated by the shaded region). There is no doubt that the diode's resistance is negative, and this is expressed as -rd.

Unique Property of Tunnel DiodesUnique Property of Tunnel DiodesIf we look at the graph, it indicates how a tunnel diode behaves when a forward voltage and current is applied to it. It is clearly evident that it has "negative resistance characteristics“.

After an initial peak, the forward current starts decreasing with an increase in the forward voltage up to a certain extent (indicated by the shaded region). There is no doubt that the diode's resistance is negative, and this is expressed as -rd.

Its Use to Generate ElectricityIts Use to Generate ElectricityWe will only discuss the general design and not go in details as the calculations

are very complicated. Due to the negative characteristic of an Esaki diode, a

charge current is generated when heat is applied to it. It can be explained in this

way: when a normal resistance R is connected to a battery, it starts discharging

(here according to Ohms law I=V/R). Therefore logically a negative resistance

should start charging the battery (now -I=V/-R). Similarly if the power dissipated in

a normal resistance is P=I2R watts, conversely a negative resistance should

generate wattage since in this case P=-I2-R. The negative sign of current (I)

indicates generation of power, and this is the operating principle of tunnel diodes.

How Tunnel Diodes FunctionA group of carefully selected tunnel diode in series when fitted

to a large heat(external) absorbing metal, can produce enough

power so as to charge a 1.2V NiCd battery. The heat applied may

be solar or any other form.

TRANSISTORS Bipolar junction Transistors (BJT) : It is a three-layer device having two junctions npn and pnp transistors are possible.

Transistor type IE IB IC VEB VCB VCE

n – p – n - + + - + +

IE is the emitter currentIC is the collector currentIB is the base currentVEB is the emitter base voltageVCB is the collector base voltage

N-P-N Bipolar Junction TransistorN-P-N Bipolar Junction Transistor

• The BE junction is forward biased whereas the CB junction is reversed biased. • The width of the depletion region of the BE junction is small as compared to that of the CB junction.• The forward bias at the BE junction reduces the barrier potential and causes the electrons to flow from

the emitter to base.• As the base is thin and lightly doped it consists of very few holes so some of the electrons from the

emitter (about 2%) recombine with the holes present in the base region and flow out of the base terminal. • This constitutes the base current, it flows due to recombination of electrons and holes (Note that the

direction of conventional current flow is opposite to that of flow of electrons). • The remaining large number of electrons will cross the reverse biased collector junction to constitute the

collector current. Thus by KCL,

Voltage Or Power AmplificationVoltage Or Power Amplification

• Base of emitter junction is forward biased.• Therefore having low resistance. • Base to collector junction is reverse biased

offering very high resistance. • The order of collector current and emitter

current is same but the collector circuit resistance is very high therefore resulting in voltage or power amplification.

• It works in three configurations

• Transistors are three terminal active devices made from different semiconductor materials that can act as either an insulator or a conductor by the application of a small signal voltage.

• The transistor’s ability to change between these two states enables it to have two basic functions: “switching” (digital electronics) or “amplification” (analogue electronics).

OPERATIONOPERATION

• Bipolar Transistors are current regulating devices that control the amount of current flowing through them in proportion to the amount of biasing voltage applied to their base terminal acting like a current-controlled switch.

• The principle of operation of the two transistor types PNP and NPN, is exactly the same the only difference being in their biasing and the polarity of the power supply for each type.

• Active Region – the transistor operates as an amplifier and Ic = β.Ib• Saturation – the transistor is “Fully-ON” operating as a switch and Ic = I(saturation)• Cut-off – the transistor is “Fully-OFF” operating as a switch and Ic = 0

OPERATIONOPERATIONActive Region

CONSTRUCTIONCONSTRUCTION

There are basically three possible ways with one terminal being

common to both the input and output.

• Common Base Configuration – has Voltage Gain but no Current

Gain.

• Common Emitter Configuration – has both Current and Voltage

Gain.

• Common Collector Configuration – has Current Gain but no

Voltage Gain.

Bipolar Transistor ConfigurationsBipolar Transistor Configurations

The Common Base (CB) ConfigurationThe Common Base (CB) Configuration

The current gain for this type of circuit is almost one.

This is a non-inverting voltage amplifier circuit, in that the signal voltages Vin and Vout are “in-phase”. High voltage gain characteristics due to a high ratio of output to input resistance or more importantly “load” resistance ( RL ) to “input” resistance ( Rin ) giving it a value of “Resistance Gain”. Then the voltage gain ( Av ) for a common base configuration is therefore given as: AV=VOUT/VIN=IC X RL/IE X RIN

The Common Emitter (CE) ConfigurationThe Common Emitter (CE) Configuration

This is mainly because the input impedance is LOW as it is connected to a forward biased PN-junction, while the output impedance is HIGH as it is taken from a reverse biased PN-junction. IE = Ic + IB. The current gain Beta, ( β ), (Ic/IB) is quite large, has a value between 20 and 200 for most general purpose transistors. Ic/Ie is called Alpha. This has a greater current and power gain and is an inverting amplifier circuit.

The common emitter amplifier configuration produces the highest current and power gain of all the three bipolar transistor configurations.

The Common Collector (CC) ConfigurationThe Common Collector (CC) ConfigurationThis type of configuration is commonly known as a Voltage Follower or Emitter Follower circuit.

It is very useful for impedance matching applications because of the very high input impedance, in the region of hundreds of thousands of Ohms while having a relatively low output impedance. The voltage gain is always less than “1” (unity).

The load resistance of the common collector transistor receives both the base and collector currents giving a large current providing good current amplification with very little voltage gain.

The Junction Field Effect The Junction Field Effect TransistorTransistor

• There are two basic configurations of junction field effect transistor, the N-channel JFET and the P-channel JFET. The N-channel JFET’s channel is doped with donor impurities meaning that the flow of current through the channel is negative (hence the term N-channel) in the form of electrons.

• Likewise, the P-channel JFET’s channel is doped with acceptor impurities meaning that the flow of current through the channel is positive (hence the term P-channel) in the form of holes.

Field Effect TransistorsField Effect Transistors

• There are two ohmic electrical connections at either end of the channel called the drain and the source.

• Within this channel there is a third electrical connection which is called the gate terminal and this can also be a p-type or n-type material forming a pn-junction with the main channel.

OperationOperation• The Field Effect Transistor, or simply FET however, uses the voltage that is applied

to their input terminal, called the Gate to control the current flowing through them resulting in the output current being proportional to the input voltage.

• As their operation relies on an electric field (hence the name field effect) generated by the input Gate voltage, this then makes the Field Effect Transistor a “VOLTAGE” operated device.

The semiconductor “channel” of the Junction Field Effect Transistor is a resistive path through which a voltage VDS causes a current ID to flow and as such the junction field effect transistor can conduct current equally well in either direction. As the channel is resistive in nature, a voltage gradient is thus formed down the length of the channel with this voltage becoming less positive as we go from the Drain terminal to the Source terminal.

The magnitude of the current flowing through the channel between the Drain and the Source terminals is controlled by a voltage applied to the Gate terminal, which is a reverse-biased. In an N-channel JFET this Gate voltage is negative while for a P-channel JFET the Gate voltage is positive. The main difference between the JFET and a BJT device is that when the JFET junction is reverse-biased the Gate current is practically zero, whereas the Base current of the BJT is always some value greater than zero.

The result is that the PN-junction therefore has a high reverse bias at the Drain terminal and a lower reverse bias at the Source terminal. This bias causes a “depletion layer” to be formed within the channel and whose width increases with the bias.

Biasing of an N-channel JFETBiasing of an N-channel JFET

Output characteristic V-I curves of a typical junction FET.Output characteristic V-I curves of a typical junction FET.

The drain current in the saturation region is often approximated in terms of gate bias as:Where IDSS is the saturation current at zero gate–source voltage, i.e. the maximum current which can flow through the FET from drain to source at any (permissible) drain-to-source voltage; see e. g. the I-V characteristics diagram above.

Silicon Controlled Rectifier- SCRSilicon Controlled Rectifier- SCRBy applying a small voltage between gate and cathode, the lower transistor will be forced on by the resulting base current, which will cause the upper transistor to conduct, which then supplies the lower transistor's base with current so that it no longer needs to be activated by a gate voltage. The necessary gate current to initiate latch-up, of course, will be much lower than the current through the SCR from cathode to anode, so the SCR does achieve a measure of amplification.

This method of securing SCR conduction is called triggering, and it is by far the most common way that SCRs are latched in actual practice.

Silicon Controlled Rectifier- SCRSilicon Controlled Rectifier- SCR

There are three modes of operation Forward blocking mode: In this mode of operation, the anode is given a positive potential while the cathode is given a negative voltage, keeping the gate at zero potential i.e. disconnected. In this case junction J1 and J3 are forward biased while J2 is reversed biased due to which only a small leakage current exists from the anode to the cathode until the applied voltage reaches its break over value, at which J2 undergoes avalanche breakdown and at this break over voltage it starts conducting, but below break over voltage it offers very high resistance to the current and is said to be in the off state.

Silicon Controlled Rectifier- SCRSilicon Controlled Rectifier- SCR

Forward conduction mode: SCR can be brought from blocking mode to conduction mode in two ways: either by increasing the voltage across anode to cathode beyond break over voltage or by applying of positive pulse at gate. Once it starts conducting, no more gate voltage is required to maintain it in the on state. There are two ways to turn it off: 1. Reduce the current through it below a minimum value called the holding current and 2. With the Gate turned off, short out the Anode and Cathode momentarily with a push-button switch or transistor across the junction.

Silicon Controlled Rectifier- SCRSilicon Controlled Rectifier- SCR

Forward voltage triggering occurs when the anode-cathode forward voltage is increased with the gate circuit opened. This is known as avalanche breakdown, during which junction J2 will breakdown. At sufficient voltages, the thyristor changes to its on state with low voltage drop and large forward current. In this case, J1 and J3 are already forward biased.

• Operational amplifiers are linear devices that have all the properties required for nearly ideal DC amplification and are therefore used extensively in signal conditioning, filtering or to perform mathematical operations such as add, subtract, integration and differentiation.

• An Operational Amplifier is basically a three-terminal device which consists of two high impedance inputs, one called the Inverting Input, marked with a negative or “minus” sign, ( - ) and the other one called the Non-inverting Input, marked with a positive or “plus” sign ( + ).

• The third terminal represents the Operational Amplifier output port which can both sink and source either a voltage or a current.

Operational Amplifier BasicsOperational Amplifier Basics

In a linear operational amplifier, the output signal is the amplification factor, known as the amplifiers gain ( A ) multiplied by the value of the input signal and depending on the nature of these input and output signals, there can be four different classifications of operational amplifier gain.•Voltage – Voltage “in” and Voltage “out”•Current – Current “in” and Current “out”•Transconductance – Voltage “in” and Current “out”•Transresistance – Current “in” and Voltage “out”

Operational Amplifier BasicsOperational Amplifier Basics

Most of the circuits dealing with operational amplifiers are voltage amplifiers. The amplified output signal of an Operational Amplifier is the difference between the two signals being applied to the two inputs. In other words the output signal is a differential signal between the two inputs and the input stage of an Operational Amplifier is in fact a differential amplifier as shown.

Operational Amplifier BasicsOperational Amplifier Basics

Operational Amplifier BasicsOperational Amplifier BasicsThe circuit operates from a dual supply +Vcc and -Vee which ensures a constant supply. The voltage that appears at the output, Vout of the amplifier is the difference between the two input signals as the two base inputs are in anti-phase with each other. As the forward bias of transistor, TR1 is increased, the forward bias of transistor TR2 is reduced and vice versa. Then if the two transistors are perfectly matched, the current flowing through the common emitter resistor, Re will remain constant.

Like the input signal, the output signal is also balanced and since the collector voltages either swing in opposite directions (anti-phase) or in the same direction (in-phase) the output voltage signal, taken from between the two collectors is, assuming a perfectly balanced circuit the zero difference between the two collector voltages.This is known as the Common Mode of Operation with the common mode gain of the amplifier being the output gain when the input is zero.

Operational Amplifiers also have one output (although there are ones with an additional differential output) of low impedance that is referenced to a common ground terminal and it should ignore any common mode signals that is, if an identical signal is applied to both the inverting and non-inverting inputs there should no change to the output.However, in real amplifiers there is always some variation and the ratio of the change to the output voltage with regards to the change in the common mode input voltage is called the Common Mode Rejection Ratio or CMRR.

Operational Amplifier BasicsOperational Amplifier Basics

Operational Amplifiers on their own have a very high open loop DC gain and by applying some form of Negative Feedback we can produce an operational amplifier circuit that has a very precise gain characteristic that is dependant only on the feedback used.• An operational amplifier only responds to the difference between the

voltages on its two input terminals, known commonly as the “Differential Input Voltage” and not to their common potential. Then if the same voltage potential is applied to both terminals the resultant output will be zero.

• An Operational Amplifiers gain is commonly known as the Open Loop Differential Gain, and is given the symbol (Ao).

Operational Amplifier BasicsOperational Amplifier Basics

Op-amp Parameter and Idealised CharacteristicOp-amp Parameter and Idealised CharacteristicOpen Loop Gain, (Avo)

Infinite – The main function of an operational amplifier is to amplify the input signal and the more open loop gain it has the better. Open-loop gain is the gain of the op-amp without positive or negative feedback and for such an amplifier the gain will be infinite but typical real values range from about 20,000 to 200,000.

Input impedance, (Zin)Infinite – Input impedance is the ratio of input voltage to input current and is assumed to be infinite to prevent any current flowing from the source supply into the amplifiers input circuitry ( Iin = 0 ). Real op-amps have input leakage currents from a few pico-amps to a few milli-amps.

Output impedance, (Zout)Zero – The output impedance of the ideal operational amplifier is assumed to be zero acting as a perfect internal voltage source with no internal resistance so that it can supply as much current as necessary to the load. This internal resistance is effectively in series with the load thereby reducing the output voltage available to the load. Real op-amps have output impedances in the 100-20kΩ range.

Bandwidth, (BW)Infinite – An ideal operational amplifier has an infinite frequency response and can amplify any frequency signal from DC to the highest AC frequencies so it is therefore assumed to have an infinite bandwidth. With real op-amps, the bandwidth is limited by the Gain-Bandwidth product (GB), which is equal to the frequency where the amplifiers gain becomes unity.

Offset Voltage, (Vio)Zero – The amplifiers output will be zero when the voltage difference between the inverting and the non-inverting inputs is zero, the same or when both inputs are grounded. Real op-amps have some amount of output offset voltage.

Op-amp Parameter and Idealised CharacteristicOp-amp Parameter and Idealised Characteristic

From these “idealized” characteristics above, we can see that the input resistance is infinite, so no current flows into either input terminal (the “current rule”) and that the differential input offset voltage is zero (the “voltage rule”). It is important to remember these two properties as they will help us understand the workings of the Operational Amplifier with regards to the analysis and design of op-amp circuits.

From this frequency response curve we can see that the product of the gain against frequency is constant at any point along the curve. Also that the unity gain (0dB) frequency also determines the gain of the amplifier at any point along the curve. This constant is generally known as the Gain Bandwidth Product or GBP. Therefore: GBP = Gain x Bandwidth or A x BW.

Op-amp Parameter and Idealised CharacteristicOp-amp Parameter and Idealised Characteristic

An Operational Amplifiers BandwidthAn Operational Amplifiers Bandwidth

The operational amplifiers bandwidth is the frequency range over which the voltage gain of the amplifier is above 70.7% or -3dB (where 0dB is the maximum) of its maximum output value as shown below.

The operational amplifiers bandwidth is the frequency range over which the voltage gain of the amplifier is above 70.7% or -3dB (where 0dB is the maximum) of its maximum output value as shown below.

We know now that an Operational amplifiers is a very high gain DC differential amplifier that uses one or more external feedback networks to control its response and characteristics. We can connect external resistors or capacitors to the op-amp in a number of different ways to form basic “building Block” circuits such as, Inverting, Non-Inverting, Voltage Follower, Summing, Differential, Integrator and Differentiator type amplifiers.

Operational Amplifiers SummaryOperational Amplifiers Summary

An “ideal” or perfect Operational Amplifier is a device with certain special characteristics such as infinite open-loop gain Ao, infinite input resistance Rin, zero output resistance Rout, infinite bandwidth 0 to ∞ and zero offset (the output is exactly zero when the input is zero).

There are a very large number of operational amplifier IC’s available to suit every possible application from standard bipolar, precision, high-speed, low-noise, high-voltage, etc, in either standard configuration or with internal Junction FET transistors.Operational amplifiers are available in IC packages of either single, dual or quad op-amps within one single device. The most commonly available and used of all operational amplifiers in basic electronic kits and projects is the industry standard μA-741.

OPAMP CONFIGURATIONSOPAMP CONFIGURATIONS

Differential Amplifier

Summing Amplifeir

Voltage Follower

Integrator Differentiator

RGB LED

Try resistors out in various combination to make different colors. Experiment by adding potentiometers to the leads.

Photoresistor

Photoresistors change their resistance by the amount of light detected.

Turn things on and off with a:

WireButtonPhotoresistorHall Effect SensorRelayTransistorButtonSwitch

Transistors

NPN Transistor

Hall Effect Sensor

Reed Switch Example

A reed switch is closed when a magnet is in close proximity.It is symmetric so it can placed either direction.

Tilt ball switch

Emergency on/off if project tips over.

Motors

Try changing the direction of the diode.What happens?

Relay

ELECTRONICS COMPONENTS AND SYMBLOS

ELECTRONICS COMPONENTS AND SYMBLOS

ELECTRONICS COMPONENTS AND SYMBLOS

ELECTRONICS COMPONENTS AND SYMBLOS

ELECTRONICS COMPONENTS AND SYMBLOS

ELECTRONICS COMPONENTS AND SYMBLOS

ELECTRONICS COMPONENTS AND SYMBLOS

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ELECTRONICS COMPONENTS AND SYMBLOS

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ELECTRONICS COMPONENTS AND SYMBLOS

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