Basic Electronics Unit-1

8/12/2019 Basic Electronics Unit-1

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Passive circuit

componentsUnit-1


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Resistance

Resistance R is

Directly proportional to its length L and inverselyproportional to area of cross section A

R= L

A

Where constant of the material known as its

specific resistance or resistivity.Unit : Ohms ()


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SYMBOL - R

UNITS - OHM ( ) ELECTRICAL -

REPRESENTATION

MATHEMATICAL - R = ( * L) /A

REPRESENTATION


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TYPES OF RESISTORSFixed resistors Variable resistors

1. Carbon composition 1. Potentiometer 1. Carbonpotentiometer

2. Wire woundpotentiometer

a. Single turnb. Multi turn

2. Carbon film 2. Rheostat

3. Metalfilm

a. Thin film 3.Trimmer

b. Thick

film

1. Tin Oxide type

2. Metal glaze type3. Cermet type4. Bulk film type

4. Wire wound 1. Power style type2. Precision style wire

wound resistor


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Fixed Resistors

Fixed resistorshave only one ohmic value, which cannotbe changed or adjusted. One type of fixed resistor is thecomposition carbon resistor.


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Carbon composition

Most widely used in discrete circuits

Made of finely divided carbon

mixed with a powdered insulating

material such as resin or clay

Then placed in plastic casing with

lead wires of tinned copper.

Available in few ohms to 100 Mega

ohms

Power rating: 1/8 to 2W


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Carbon Film Resistor


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Carbon film Manufactured by depositing a carbon film on a ceramic

substrate

Only approximate values of R are obtained by either

trimming the layer thickness or by cutting helical grooves of

suitable pitch along its length Cutting of grooves is stopped as soon as desired value of

resistance is obtained

Contact caps are fitted at both ends Lead wires made of tinned copper are welded to end caps

Range: 10to 10M

Power rating: 2W, less noisy, low cost


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Metal film resistor

Construction similar to carbon film resistor Film usually consists of an alloy of tin and

antimony metals

Available as thin and thick film typecomponents


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a. Thin film resistor

Film has a thickness of order of one millionthof an inch

Thin film is deposited on a ceramic substrateunder high vacuum deposition

Metals used for deposition Nickel andchromium

Range: 10to 1M

Power rating: up to 5W


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b. Thick film resistor Film thickness greater than one millionth of an

inchTin oxide Metal glaze Cermet Bulk film

Tin oxide in vapour

form is deposited on a

ceramic substrate

under high T, whichresults in a tightly

formed resistance film.

Powder glass and fine metal

particle(palladium and

silver) is deposited on

ceramic substrate, heated to800oC, results in a fusion

of metal particles to thesubstrate.

Mixture of precious

metals and binder

materials on ceramic

substrate, heated to highT.

Derived from ceramicand metal.

Metal film is etched on

glass substrate. As metal

film and glass have

unequal coefficients ofexpansion, metal film is

compressed by glasssubstrate. Compressed

film has ve Temp.

Coeff. which cancels

+ve Temp Coeff., result

in temp. coefficient of R

close to zero.

Range: Few ohms to2.5M

Few ohms to 1.5M 10to 10M 30to 600K

Power rating: up to

2 W

Up to 5W 3W 1W


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Wire Wound Resistor

Special resistance wireis wrappedaround an insulating core, typicallyporcelain, cement, or pressedpaper.

These resistors are typically usedfor high-current applications withlow resistance and appreciablepower.

Fig. : Large wire-wound resistors with 50-W power ratings.(a) Fixed R, length of 5 in. (b) Variable R, diameter of 3 in.


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Wire wound resistor

Two types:

Power style

Precision style


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Power style

Made by winding a single layer length of special alloy wire,in the form of coil around an insulating core.

Ends of winding are attached to metal pieces to which

tinned copper wire leads.

Covered with vitreous enamel or silicone coating, whichprotects against moisture and breakage.

Alloys used nickel-chromium-aluminium & nickel-

chromium-iron (Nichrome)

Core is ceramic, steatite or vitreous material M

Power rating: 1500W


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Precision style Wound on ceramic tubes or epoxy moulded tubes

Wire is wound in alternate directions in adjacent

sections to minimize inductive effect at high

Frequencies.

This winding is called bifilar

Ohm to M;

Power rating : 2W


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Variable Resistor Examples


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Variable Resistors

A variable resistor is a resistor whose resistancevalue can be changed. (zero to certain maximumvalue.

They are used in electronic circuits to adjust valuesof voltages and currents.

Ex: volume control in radio.

brightness control in TV.


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It can be classified into three types

a. Potentiometer

b. Rheostat

c. Trimmer

Variable resistors


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Potentiometers

Potentiometers:

Three terminals.

Ends connected across the voltage source.

Third variable arm taps off part of the voltage.


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Variable Resistors

Potentiometersarealso called as POTS

There is a fixed valueof resistance betweentwo terminals(1,3)

For VariableResistance (1,2)should be connected

1

32


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Potentiometer

Referred as POT

Two types: Carbon potentiometer

Wire wound potentiometer

Single turn wire wound potentiometer

Multi turn wire wound potentiometer


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Carbon potentiometer


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Consists of an of annular ring of carbon resistance, formed

on plastic base, over which movable contact can slide and

attached to shaftwhich runs through center of base.

Slip ring(continuous metal ring) contacted to movable

contact.

Two terminals connected to end of carbon track

One terminal connected to slip ring

Assembly is enclosed by sheet metal over which resistance

value and taper is engraved.

Taper-variation in R along the track.

Manufactured either in film or moulded track types.


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Film type

Mixture of carbon, graphite and resin sprayed

on phenolic sheet,with suitable marks in ring

form.

Moulded type

Integral moulding of base, track and terminals Gets rids of solders, rivets, welds

Very fewer mechanical joints


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Single turn Resistancewireis wound on a flat strip of insulating card

made of flexible plastics or anodized aluminum and strip

is bent round a cylindrical surface. Copper alloy wire-low resistance pots

Nickel chromium high resistance pots

Slider metal or beryllium copper contact is made inside

periphery or outer edge. Range : 50to 5M

Power ratings: 2 to 3W

Uses : gain control element in an amplifier

Brightness and contrast controls in TV receivers


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Multi turn/helical pots

Used in precise setting of a resistancevalue.

eg. Setting coefficient in analog computer. Resistance element is wound on long strip and

formed into helix and held in a plane usingsilicone varnish.

Contact used isprecision metal.

Has stray inductance and capacitance-problem athigh frequency operation.

Range: 50to 250k

Power rating: up to 5 W


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Rheostat

Rheostatsandpotentiometersare variable resistances used tovary the amount of current or voltage in a circuit.

Rheostats:

Two terminals.

Connected in series with the load and the voltage source.


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Rheostat

Wire wound pot Dissipate more than 5W

Wire wound on open tube of ceramic , covered with

vitreous enamel, except for the track of the movable

contact. Withstand temperatures upto 300oC

Used to control

Motor speed

X-ray tube voltages

Welding current

Ovens

High power applications


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Rheostats

Using a Rheostat to Control Current Flow,


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Trimmer


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Trimmer

Uses: R must be adjustable but not continuously variable.

Calibration

Balancing of electronic equipment Screw activated and R adjusted by a screw driver.

Resistance track made of carbon and cermet

Carbon track along with movable slide housed in steelcasing.

Range: Few ohms to 5M

Power ratings: 1W


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Tolerance

Acceptable deviation in resistance value.

Ordinaryresistors- 5%, 10% and 20%

Precisionresistors close to 0.1% Eg: resistor 1k with 10% tolerance can have

value between 900 and 1100


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Resistor Color Coding

Carbon resistors are small, so their R value in

ohms is marked using a color-coding system.

Colors represent numerical values.

Coding is standardized by the Electronic

Industries Alliance (EIA).


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RESISTOR COLOR CODES

BLACK=0 GREEN = 5BROWN=1 BLUE = 6

RED = 2 VIOLET = 7

ORANGE = 3 GREY = 8

YELLOW = 4 WHITE = 9

BBROY Great Britain Very Good Wife


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Resistor Color Code

0 Black

1 Brown

2 Red

3 Orange

4 Yellow

5 Green

6 Blue

7 Violet

8 Gray

9 White

Color Code

Fig:How to read color stripes on carbon

resistors for Rin ohms.


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Resistors under 10 :

The multiplier band is either gold or silver.

For gold, multiply by 0.1.

For silver, multiply by 0.01.


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Applying the ColorCode

The amount bywhich the actual R

can differ from thecolor-coded value isits tolerance.Tolerance is usually

stated inpercentages.

00 is the nominal value.4 7

Violet = 7

Red = 2

Gold = 5%

5% of 4700 = 235

4700 + 235 = 4935

4700 - 235 = 4465

The actual value can range from 4465 to 4935 .

00 is the nominal value.4 700 is the nominal value.4 00 is the nominal value.00 is the nominal value.4 7

Violet = 7

Red = 2

Gold = 5%

5% of 4700 = 235

4700 + 235 = 4935

4700 - 235 = 4465

Violet = 7

Red = 2

Gold = 5%

5% of 4700 = 235

4700 + 235 = 4935

4700 - 235 = 4465

The actual value can range from 4465 to 4935 .

Yellow = 4


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Colour Coding Example

Resistor colour code calculation

The first band red has a valueof 2

The second band violet has a

value of 7

The third band has a multiplierof x 10

The last band indicates a

tolerance value of +/-5%

Resistance value is 270 +/-5%

2

7

x10

+/-5%


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What is the nominal value and permissibleohmic range for each resistor shown?


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What is the nominal value and permissibleohmic range for each resistor shown?

1 k(950 to 1050 )

390 (370.5 to 409.5 )

22 k(20.9 to 23.1 k)

1 M

(950 k

to 1.05 M

)


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Standard Resistor ValuesElectronic Industries Association (EIA) standard E24:

Standard E24 specifies resistors based on 5% tolerance (often resistor of this category has2% tolerance now a days due to advancement of manufacturing techniques)

100 110 120 130 150 160 180 200

220 240 270 300 330 360 390 430

470 510 560 620 680 750 820 910

Standard Resistor values =

10M Ohms

(Where M can be any integer, positive or negative)

For other standards:http://www.logwell.com/tech/components/resistor_values.html
http://www.logwell.com/tech/components/resistor_values.htmlhttp://www.logwell.com/tech/components/resistor_values.html


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Capacitor Examples

http://www.wordiq.com/definition/Image:Condensators.JPG

Source: Basic Electronics, Bernard Grob

Through-HoleSMT Chip

Capacitor

Network
http://www.wordiq.com/definition/Image:Condensators.JPGhttp://www.johansondielectrics.com/http://www.wordiq.com/definition/Image:Condensators.JPG


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Capacitors

Basic capacitor construction

Dielectricmaterial

Plate 1

Plate 2The dielectricmaterial is aninsulator thereforeno current flowsthrough thecapacitor


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Capacitors

A basic capacitor has two parallel platesseparated by an insulating material

A capacitor stores an electrical chargebetween the two plates

The unit of capacitance is Farads (F)

Capacitance values are normally smaller, suchas F, nF or pF


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Capacitors Store electric charge

Uses:

Tuned circuits

Timing circuits

Filters Amplifier circuits

Oscillator circuits

Relay

Power factor correction Starting single phase motors


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Contd

Reactance of a capacitor a frequency f is

Xc=1/(2fC)

Capacitor allows higher frequency currents more

easily than lower frequency currents

For d.c voltages: f=0 and Xc=,capacitor block d.c

voltages or currents.


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Capacitor

Has two conducting plates separated bydielectric material

Capacitance C =0rA/d

Area = Area of each plate (m2

) ddistance between parallel plates in m

0permittivity of free space = 8.854x10-12F/m

rrelative dielectric constant (permittivity)


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Contd

Dielectric strength-ability of a dielectric to withstand a

potential difference without breakdown.

Capacitors classified according to dielectric used.

Dielectric used:

Air

Electrolyte

Ceramic

Plastic Mica

paper


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Fixed Capacitors

1) Electrolytic Capacitors

Smallest volume and cost

Used in applications such as filter in a power supply,

time constant circuits, bypass, coupling/decoupling,

smoothing and power electronic applications

Manufactured-0.1F upto 1.0 F & upto 500V dc.

A)Polarized and Non-Polarized

Polarizedcan be used for dc applications only Non-polarized - used in motor start applications

Types : Aluminium, Tantalum(based on the metal used)


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Capacitors

Types of capacitors

The dielectricmaterialdetermines the type ofcapacitor

Common types ofcapacitors are:

Mica

Ceramic

Plastic film


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Capacitors

Some capacitors arepolarised, they canonly be connected

one way around Electrolytic

capacitors arepolarised


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Polarized Electrolytic Capacitor


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Polarised Vs Non-Polarised


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Polarized Electrolytic Capacitor

Certain metals like aluminium, tantalum,

vanadium & bismuth are used to form anode and

cathode foils

Thin layer of aluminium or tantalum oxide iselectrochemically formed on anode foil.

Oxide layerdielectric

Cathode and oxide coated anode is separated by

paper space which is soaked in electrolytic solution

High voltage capacitors have spacer thicker than

low voltage capacitors

Common type: roller type

Non polarised Electrol tic


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Non-polarised Electrolytic

CapacitorThis type has two oxide coated anodes

Has one half the capacitance for same

voltage rating of equal sized polarised

capacitor

Uses:

Motor starting

Cross over networks

Large pulse signals

Types of NP Electrolytic


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Types of NP Electrolytic

CapacitorAluminium typeavailable in polarised & NP

Tantalum type

Foil

Wet anode

Solid anode


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Aluminium type

Available in polarised or non-polarised

High DC leakage and low insulation

resistance

Advantage:

Low cost, high volumetric efficiency

Disadvantage Limited Shell life

Capacitance deteriorates with time and use


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Tantalum type

Advantage:

Long shell life

Stable operating characteristics

Increased operating temperature range

Greater volumetric efficiency

Disadvantage: High cost

Low voltage rating

Tantalum Wet anode Vs Solid Anode


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TantalumWet anode Vs Solid Anode

Tantalum electrolytic capacitors


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Tantalum electrolytic capacitors Foil type:similar to aluminium foil type

Wet anode type: Made by moulding mixture of tantalum powder and binder into

pellet shape under high Temp.

Tantalum oxide is electrochemically formed over the anode pellet.

Volumetric efficiency is thrice that of foil type

Solid anode type:

Made by sintering(removing impurities) anode pellet on whichtantalum oxide is formed

Pellet is formed with manganese dioxide layer that serves as soliddielectric

Cathode is made by coating pellet by carbon and silver paint

Longest life and lowest leakage current.


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Ceramic capacitors

Use ceramic dielectric with thin metal films aselectrodes bonded to ceramic

Types

Low permittivity Medium permittivity

High permittivity


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Low permittivity

Has zero temp. coefficient

Used in temp. compensation networks

Permittivity ranges from 6 to 400

Operates at 6KV and temp. up to 125oC

C: 0.001F

M di i i i


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Medium permittivity Permittivity : 500 to 4000..

Stable over temp. range of -55 to +125oC

High permittivity

Disadvantage:

The capacitance values changes with increase in

temp ,DC voltage and frequency.

Permittivity : 5000 to 30000.. C: 2.2F

Maximum working voltage:100V


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Ceramic capacitors

Types

Disc

Tubular

Monolithic

Barrier


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Disc capacitors

Ceramic sheets are baked and cut into 0.5mm

Silver on both sides to form conduction plates

Terminal leads are fixed by soldering

Encapsulated in plastic or phenolic moulding

Have high capacitance/unit volume

High voltage operations

C: 0.01F

Voltage rating: 750V dc, 350V ac

T b l i


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Tubular capacitor

Required materials arepowdered & pressed, fixedwith fluxes and moulded into tubes

Leads are soldered

C: 5pF to 1000pF for 5KV & 10000pF for lowvoltages

Monolithic capacitor


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The monolithic capacitors is formed by interleaving

layers of ceramic and platinum electrodes.



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First step is preparation of slurry or slip in either aqueous

or organic solution

Organic binders and plasticizers are added to slurry to give

strength & flexibility to film

Cast on a carrier substrate in thickness of 0.025mm to

0.75mm and cut into strips

Apply electrodes of platinum or palladium to the film

After the required number of layers have been formed for

specific value, strips are subjected to consolidation under

pressure

Structure is fired to form monolithic block

Sintering is done at 1300oC to reduce volume of block by

40%


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Barrier Layer Capacitor DielectricBarium titanate

Ceramic disc reduced at 1300oC becomes non

conducting

If re-oxidised conducting layer of ceramic forms

upon the surface This barrier of conducting to non-conducting has

high values of dielectric constants

Silver electrodes are fired on this barrier and entireassembly is reoxidised in hot air prevents

moisture

Low voltage & high frequency applications

Tem :- -40oC to 80oC


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Uses of Ceramic capacitors

By pass capacitors

Decoupling and biasing applications

TV receivers

To isolate antenna in receivers (tubular)

Drawback Capacitance varies with temp


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Plastic Capacitors

Dielectric plastic i.e. polystyrene, polycarbonate,teflon & polyester(mylar)

Range: 500pF to 10F

If sealed properly, exhibits good mechanical strength,

resistance to heat and chemical inertness

Characteristics

High insulation resistance

High reliability

Small size

Low dielectric absorption


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Plastic capacitors

Types

Polystyrene

Polyester

Polycarbonate

Polystyrene capacitor


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Polystyrene capacitor

Low permittivity than polyester and poly

carbonate

Polystyrene film is rolled with aluminium foils

Heated to soften the plastic to make good contact

with metal foil Disadvantage: Low tensile strength, large size

Advantage: Small capacitance change with Temp,

good stability, low dissipation factor

Maximum operating T: 85oC

Uses: coupling, resonant , measuring circuits, AC

applications


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Polyester Capacitors

Characteristics: Tough polymerwith high tensile strength

Good insulating properties with T change

Low moisture absorption

Maximum operating T: 125oC

Mostly wide used film (good mechanical & Electrical

properties)

Applications: Coupling/decoupling at low and medium Freq

Power electronics

Ideal for DC applications


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Poly carbonate capacitors

Polyester of carbonic acid bisphenols

Low dissipation factor

High insulation resistance

T: 125oC

Small size

Stable Long life capacitor

Mainly for DC and also AC applications

Mica capacitors


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Mica capacitors Dielectric: muscovite or white mica, ruby or rose colored

mica, amber mica

Dielectric constant3 to 8

Dielectric strength6001500V/mil

Breakdown voltage: 500V to 20kV

Low loss, T: 400oC

Better temp. coefficient, frequency characteristic

Highly stable

Good for cheap and rugged capacitor

Uses: coupling capacitors at high F radio transmitters,measuring circuits, bypassing circuits, RF resonant

circuits

Drawback:

Big size, absorbs moisture


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Mica capacitors

Types

Stacked Mica

Silvered Mica

d


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Stacked Mica Capacitor

S k d Mi C i


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Stacked Mica Capacitor

Mica sheets are selected and stacked

between tin foil sections

Stacking done under controlled pressure

Alternate metal foils connected to form leads

T : -55 to + 150oC

High insulation resistance Capacitance : 1pF to 0.1F

Sil d Mi C i


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Silvered Mica Capacitor

Sil d Mi C i


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Silvered Mica Capacitor

Made of stacked silver coated mica sheets

placed alternatively and sealed in wax

modulated case

Coating of mica is done at 500oC with silver

oxide solution

Small size

Good mechanical stability

P i


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Paper capacitors

Dielectric Kraft paper impregnated withwax or resin

Rolled sandwich package

Range: 500pF to 50F

T:125oC

Withstand high voltages, cheap

Types:

Impregnated paper capacitor

Metallised paper capacitor

P i


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Paper capacitors

Types

Impregnated Paper

Metallised Paper

I d P C i


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Impregnated Paper Capacitor Two thin sheets of paper between metal foils

rolled and impregnated with

mineral oil, wax, petroleum jelly, castor oil,

chlorinated diphenyl, etc

Construction: - tab, extended foil

Tab: metal tab is inserted after rolling, lead

wires are soldered to tab

Extended foil: sheets of foil extends over paper

margin. inexpensive, high voltage apps, need

more space

M lli d i


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Metallised paper capacitor

Thin layer of metal (50 microns) sprayed on paperwithstand 200V

Rolled capacitor is impregnated and enclosed in

metal case Low insulation R, power factor

Needs less space

Uses :

Power factor correction, motor starting, bypass and filter

capacitors in AF apps

V i bl C i


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Variable Capacitor

V i bl C i


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Variable Capacitor

V i bl C i


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Variable Capacitor

Has two set of aluminium plates

One mounted on shaftrotor

Another - fixed platesstator

Two are insulatednot to contact each other

When shaft rotates, area between rotor and

stator varies, capacitance varies

Range: few pF to 500pF

V: 9KV60kV

V i bl C it


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Variable Capacitor

Applications : Variable capacitors are used in

communication equipment, radios,

televisions and VCRs They can be adjusted by consumers by

tuning controls

Standard Capacitor Values


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Standard Capacitor Values

Ref: http://www.aoc.nrao.edu/~pharden/ref/_caps.pdf

I d t
http://www.aoc.nrao.edu/~pharden/ref/_caps.pdfhttp://www.aoc.nrao.edu/~pharden/ref/_caps.pdf


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Inductors


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Documents

Basic Electronics Unit-1