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ELECTRICITY

good slave of man

a very bad master

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Teka teki..

"Kenapa lelaki perlu beristeri tiga... .

SENYUM pada orang tua tanda sayang.

SENYUM pada kanak-kanak tanda kasih.SENYUM pada kekasih tanda cinta.

SENYUM depan telefon tanda gila,

masih SENYUM lagi... memang sah GILA!

Jawapannya kerana :

kerana kalau kawin satu isONE

kalau kawin dua isTWO

kalau kawin tiga barulah isTERI... ..

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WEEK 1

electronicmade simple!!!

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Robert Boylestad

Digital ElectronicsCopyright 2002 by Pearson Education, Inc.

Upper Saddle River, New Jersey 07458

All rights reserved.

Chapter 1:Semiconductor Diodes

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Robert Boylestad

Digital ElectronicsCopyright 2002 by Pearson Education, Inc.



Diodes

Simplest Semiconductor Device

It is a 2-terminal device

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Various types of junction diodes.[(a) Courtesy of Motorola Inc.; and (b) and (c) Courtesy International Rectifier Corporation.]

Robert L. Boylestad and Louis Nashelsky

Electronic Devices and Circuit Theory, 8eCopyright 2002 by Pearson Education, Inc.



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Light Emitting Diode (LED)

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LED Applications

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Diode Packages

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Bridge rectifiers

They have four leads or terminals: the two

DC outputs are labelled + and -, the two AC

inputs are labelled

.

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webpage http://www.allaboutcircuits.com/vol_3/chpt_3/1.html

http://www.st-andrews.ac.uk/~www_pa/Scots_Guide/

info/comp/passive/diode/diode.htm

http://www.howstuffworks.com/diode.htm

http://www.ecawa.asn.au/home/jfuller/electronics/diodes.htm

tera.yonsei.ac.kr/class/2006_2/lecture/Lect%203%20PN%20Junction%20Diode.pdf

http://www.kpsec.freeuk.com/components/diode.htm

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You Might Be An

Engineer If... You have no life - and you can PROVE it mathematically.

You know vector calculus but you can't remember how to do long division.

You know how to integrate a chicken and can take the derivative of water.

You think in "math".

You can't remember what's behind the door in the engineering building whichsays "Exit".

When your professor asks you where your homework is, you claim to have

accidentally determined its momentum so precisely, that according to

Heisenberg it could be anywhere in the universe.

The "fun" center of your brain has deteriorated from lack of use.

You'll assume that a "horse" is a "sphere" in order to make the math easier.

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What is a Diode?

A diode is the simplest sort ofsemiconductor device

materialw

ith a varying ability to conductelectrical current

An electronic device that restrictscurrent flow chiefly to one direction.

A two-terminal semiconductor deviceused chiefly as a rectifier.

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circuit symbolThe circuit symbol

for a diode together

with commonconventions for

current through the

diode and voltage

across the diode.

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Polarity

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Function Diodes allow electricity to flow in

only one direction. The arrow of the circuit symbol shows

the direction in which the current canflow.

Diodes are the electrical version of a

valve and early diodesw

ere actuallycalled valves.

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Applications

Radio demodulation demodulation of amplitude modulated

(AM) radio broadcastsPower conversion convert alternating current (AC)

electricity into direct current (DC). Over-voltage protection

conduct damaging high voltages awayfrom sensitive electronic devices

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Applications Logic gates

Diodes can be combined with other components toconstruct AND and OR logic gates

Ionizing radiation detectors Semiconductor detectors for high energy particles

Temperature measuring Silicon bandgap temperature sensor.

Current steering prevent currents in unintended directions

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Diodes characteristics two terminal devices current is not linearly related to

voltage passive devices ie consume power

Diodes are nonlinear, t

wo terminal,passive electrical devices

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Diode Water Analogy

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Diode & check valve

Hydraulic check valve analogy: (a)Electron currentflow permitted. (b) Current flow prohibited.

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Basic operation

conducts current in only

one direction

open circuit the

opposite direction

with electrons flowing from the N-type end to the P-type

end.(ie from the "Cathode" to the "Anode")

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Robert BoylestadDigital Electronics

Copyright 2002 by Pearson Education, Inc.



Basic operation

and acts like an open in the opposite direction

Ideally it conducts current in only one direction

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Diode IV Curve

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The graph shows how currentdepend upon voltage for a diode.

When the voltage across the

diode is positive, a lot of

current can flow once the

voltage becomes largeenough.

When the voltage across the

diode is negative, virtually

no current flows.

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The ideal diode model.Instead of the actual voltage-current curve

for the diode shown in the thin, lighter red,

curved line below, we're going to imagine

that the diode has the voltage-current

curve shown in the thicker, dark red lines.

When current is flowing, this approximate

model predicts no voltage across the

diode. In this situation, we say that the

diode is ON.

When the voltage across the diode is

negative, this approximate model predicts

no current flowing through the diode. In

this situation, we say that the diode is OFF.

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simplified model for the diode

When the diode is ON, it has no voltage across it so it acts like a short

circuit!

the current through the diode is positive, and the

voltage across the diode is zero. When the diode is OFF,

current is zero, so it acts like an open circuit!

the voltage across the diode is negative, and the

current through the diode is zero.

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Forward Voltage DropElectricity uses up a little energy pushing its

way through the diode, rather like a person

pushing through a door with a spring. This

means that there is a small voltage across a

conducting diode, it is called the forwardvoltage drop and is about 0.7V for all

normal diodes which are made from silicon.

The forward voltage drop of a diode is

almost constant whatever the current

passing through the diode so they have avery steep characteristic (current-voltage

graph).

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Copyright 2002 by Pearson Education, Inc.



Characteristics ofan ideal diode:

Conduction Region

Look at the vertical line!

In the conduction region, ideally

the voltage across the diode is 0V,

the current is g,

the forward resistance (RF) is defined as RF = VF/IF,

the diode acts like a short.

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Reverse VoltageWhen a reverse voltage is applied a perfect diode

does not conduct, but all real diodes leak a very tiny

current of a few A or less. This can be ignored in

most circuits because it will be very much smaller

than the current flowing in the forward direction.However, all diodes have a maximum reverse

voltage (usually 50V or more) and if this is exceeded

the diode will fail and pass a large current in the

reverse direction, this is called breakdown.

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Copyright 2002 by Pearson Education, Inc.Upper Saddle River, New Jersey 07458


Characteristics ofan ideal diode: Non-

Conduction Region

Look at the horizontal line!

In the non-conduction region, ideally

all of the voltage is across the diode,

the current is 0A,

the reverse resistance (RR) is defined as RR= VR/IR,

the diode acts like open.

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Ordinary diodes can be

split into two types: Signal diodes which pass small currents of

100mA or less and

Rectifier diodes which can pass large currents.

In addition there are LEDs and Zener diodes

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many different forms of diodes

'point-contact' signal diodes

multi-coloured light emitting diodes Power Diodes

Zener Diodes

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types of junction diodesSignal diodes (small current)

Signal diodes are used to process information (electrical signals) in

circuits, so they are only required to pass small currents of up to

100mA.

Rectifier diodes (large current)

Rectifier diodes are used in power supplies to convert alternating

current (AC) to direct current (DC), a process called rectification.

They are also used elsewhere in circuits where a large current

must pass through the diode.

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Semiconductor Materials

Common materials used in the

development of semiconductor devices:

Silicon (Si)

Germanium (Ge)

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Doping

The electrical characteristics of Silicon andGermanium are improved by adding materials in a

process called doping.

The additional materials are in two types:

n-type

p-type

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n-type materials

make the Silicon (or Germanium) atoms more negative.

p-type materials

make the Silicon (or Germanium) atoms more positive.

Join n-type and p-type doped Silicon (or Germanium) to form

a p-n junction.

n-type versus p-type

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Operating Conditions

No Bias

Forward Bias Reverse Bias

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No external voltage is applied:VD = 0V and no current is flowing ID = 0A.

No Bias Condition

Only a modest depletion layer exists.

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If a reverse-biasing voltage is applied

across the P-N junction, this depletionregion expands, further resisting anycurrent through it. (Figure below)

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Reverse Bias Condition

External voltage is applied across the p-

n junction in the opposite polarity of

the p- and n-type materials.

This causes the depletion layer to

widen. The electrons in the n-type

material are attracted towards the

positive terminal and the holes in the

p-type material are attracted towards

the negative terminal.

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Forward Bias Condition

External voltage is applied across the

p-n junction in the same polarity of

the p- and n-type materials.

The depletion layer is narrow. The

electrons from the n-type material

and holes from the p-type material

have sufficient energy to cross the

junction.

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When a forward-biasing voltage is applied across the P-N junction, the depletion region collapses becoming

thinner. The diode becomes less resistive to currentthrough it. In order for a sustained current to gothrough the diode; though, the depletion region must befully collapsed by the applied voltage. This takes acertain minimum voltage to accomplish, called the

forw

ard voltage

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Actual Diode Characteristics

Note the regions for

No Bias,

Reverse Bias, andForward Bias conditions.

Look closely at the scale for

each of these conditions!

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Diode Characteristics

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Diodecurve:showingkneeat 0.7 VforwardbiasforSi,andreversebreakdown

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Another detail about the diode is

the useful Zener region.

The diode is in the reverse bias

condition.

At some point the reverse biasvoltage is so large the diode breaks

down.

The reverse current increases

dramatically.This maximum voltage is called

avalanche breakdown voltage and

the current is called avalanche

current.

Zener Region

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The point at which the diode changes from No Bias

condition to Forward Bias condition happens when

the electron and holes are given sufficient energy to

cross the p-n junction. This energy comes from the

external voltage applied across the diode.

The Forward bias voltage required for a

Silicon diode VT $ 0.7V

Germanium diode VT $ 0.3V

Forward Bias Voltage

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As temperature increases it adds energy to the

diode.

It reduces the required Forward bias voltage

in Forward Bias condition.

It increases the amount of Reverse current inReverse Bias condition.

It increases maximum Reverse Bias

Avalanche Voltage.

Germanium diodes are more sensitive to

temperature variations than Silicon Diodes.

Temperature Effects

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Data about a diode is presented uniformly for many different diodes.

This makes cross-matching of diodes for replacement or design easier.

1. VF, forward voltage at a specific current and temperature

2. IF, maximum forward current at a specific temperature

3. IR

, maximum reverse current at a specific temperature

4. PIV or PRV or V(BR), maximum reverse voltage at a specific temperature

5. Power Dissipation, maximum power dissipated at a specific temperature

6. C, Capacitance levels in reverse bias

7. trr, reverse recovery time

8. Temperatures, operating and storage temperature ranges

Diode Specification Sheets

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typical diode parameters

Maximum repetitive reverse voltage = VRRM, the maximumamount of voltage the diode can withstand in reverse-bias mode,in repeated pulses. Ideally, this figure would be infinite.

Maximum DC reverse voltage = VR

or VDC

, the maximum amountof voltage the diode can withstand in reverse-bias mode on acontinual basis. Ideally, this figure would be infinite.

Maximum forward voltage = VF, usually specified at the diode'srated forward current. Ideally, this figure would be zero: the diode

providing no opposition whatsoever to forward current. In reality,the forward voltage is described by the diode equation.

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typical diode parameters Maximum (average) forward current = IF(AV), the maximum average

amount of current the diode is able to conduct in forward bias mode.This is fundamentally a thermal limitation: how much heat can the PN

junction handle, given that dissipation power is equal to current (I)multiplied by voltage (V or E) and forward voltage is dependent uponboth current and junction temperature. Ideally, this figure would be

infinite.

Maximum (peak or surge) forward current = IFSM or if(surge), the maximumpeak amount of current the diode is able to conduct in forward biasmode. Again, this rating is limited by the diode junction's thermalcapacity, and is usually much higher than the average current rating due

to thermal inertia (the fact that it takes a finite amount of time for thediode to reach maximum temperature for a given current). Ideally, thisfigure would be infinite.

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Anode is abbreviated A

Cathode is abbreviated K

(because the Cathode end of the diode symbol looks

like a backwards K)

Diode Symbol and Notation

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Robert BoylestadDigital ElectronicsCopyright 2002 by Pearson Education, Inc.



A. Diode Checker

B. Ohmmeter

C. Curve Tracer

Diode Testing

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Robert BoylestadDigital ElectronicsCopyright 2002 by Pearson Education, Inc.



A. Diode Checker

Many DMMs have a diode checking function.

A normal diode will exhibit its Forward Bias

voltage (VF).

The diode should be tested out of circuit.

Silicon diode $ 0.7VGermanium diode $ 0.3V

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voltage drop over diodes "Normal" diodes:

Have a voltage drop between 0.6V and 0.7V

Schottky diodes:

They have a low voltage drop (about 0.1V to 0.2V)

Light emitting diodes (LED):

These diodes will emit a light when passing current. Their voltage drop will depend on the colour of the LED, but is

around 2V to 3V.

Zener diodes:

They behave as a normal diode for current flowing from the left

to right, but will allow current to flow from the right to left if the

voltage is high enough. You get a lot ofdifferent Zener voltage diodes, e.g. 4.7V and

12V.

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Digitaldisplay meterwith diode

checkingcapability.(CourtesyComputronicsTechnology, Inc.)

Robert L. Boylestad and Louis NashelskyElectronic Devices and Circuit Theory, 8e Copyright 2002 by Pearson Education, Inc.Upper Saddle River, New Jersey 07458


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MeterwithaDiodecheckfunction

displaystheforwardvoltagedropof0.548voltsinsteadofalowresistance

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IncircuitMeasurements:

Diode circuit voltage measurements:

(a) Forward biased. (b) Reverse biased.

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IncircuitMeasurements:

A forward-biased diode

conducts current and drops a small voltage across it,

leaving most of the battery voltage dropped across

the lamp.If the battery's polarity is reversed,

the diode becomes reverse-biased, and drops allof

the battery's voltage

leaving none for the lamp.

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Robert BoylestadDigital Electronics Copyright 2002 by Pearson Education, Inc.Upper Saddle River, New Jersey 07458All rights reserved.

An ohmmeter set on a low ohms scale can be

used to test a diode.

A normal diode will have the following readings.

The diode should be tested out of circuit.

B. Ohmmeter

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B. Ohmmeter

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Curvetracer.(Courtesy of Tektronix, Inc.)


Electronic Devices and Circuit Theory, 8e Copyright 2002 by Pearson Education, Inc.Upper Saddle River, New Jersey 07458All rights reserved.

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Robert Boylestad

Digital Electronics Copyright 2002 by Pearson Education, Inc.Upper Saddle River, New Jersey 07458All rights reserved.

C. Curve Tracer

A curve tracer is a specialized type of test equipment. It will display the characteristic

curve of the diode in the test circuit. This curve can be compared to the specifications

of the diode from a data sheet.

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REVIEW:

A diode is an electrical component acting as a one-wayvalve for current.

When voltage is applied across a diode in such a way thatthe diode allows current, the diode is said to be forward-biased.

When voltage is applied across a diode in such a way thatthe diode prohibits current, the diode is said to be reverse-biased.

The voltage dropped across a conducting, forward-biaseddiode is called the forward voltage. Forward voltage for a

diode varies only slightly for changes in forward currentand temperature, and is fixed by the chemical compositionof the P-N junction.

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REVIEW:

Silicon diodes have a forward voltage ofapproximately 0.7 volts.

Germanium diodes have a forward voltage ofapproximately 0.3 volts.

The maximum reverse-bias voltage that a diodecan withstand without breaking down is calledthe Peak Inverse Voltage, or PIVrating.

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Robert Boylestad

Digital Electronics Copyright 2002 by Pearson Education, Inc.Upper Saddle River, New Jersey 07458All rights reserved.

A zener is a diode operated in

reverse bias at the Peak Inverse

Voltage (PIV) called the Zener

Voltage (VZ).

1. Zener Diode

Common Zener Voltages: 1.8V to 200V

Symbol

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What is a Zener Diode?

AZener Diode is a special kind of diode which permits current to flow

in the forward direction as normal, but will also allow it to flow in the

reverse direction when the voltage is above a certain value - the

breakdown voltage known as the Zener voltage.

The Zener voltage of a standard diode is high, but if a reverse current

above that value is allowed to pass through it, the diode is permanentlydamaged. Zener diodes are designed so that their zener voltage is much

lower - for example just 2.4 Volts.When a reverse current above the

Zener voltage passes through a Zener diode, there is a controlled

breakdown which does not damage the diode. The voltage drop across

the Zener diode is equal to the Zener voltage of that diode no matter

how high the reverse bias voltage is above the Zener voltage.

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The illustration of Current vs. Voltage

graph shows this phenomenon.With azener diode connected in the forward

direction, it behaves exactly the same as

a standard diode - i.e. a small voltage

drop of 0.3 to 0.7V with current flowing

through pretty much unrestricted. In the

reverse direction however there is a very

small leakage currentbetween 0V and

the Zener voltage - i.e. just a tiny amount

of current is able to flow. Then, when the

voltage reaches the breakdown voltage

(Vz), suddenly current can flow freelythrough it.

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Zener diodes

Zener diodes are used to maintain a fixed voltage. They are designed

to 'breakdown' in a reliable and non-destructive way so that they can

be used in reverse to maintain a fixed voltage across their terminals

Zener diodes can be distinguished from ordinary diodes by their codeand breakdown voltage which are printed on them. Zener diode codes

begin BZX... or BZY... Their breakdown voltage is printed with V in

place of a decimal point, so 4V7 means 4.7V for example.

Zener diodes are rated by their breakdown voltage and maximum

power:

The minimum voltage available is 2.4V.

Power ratings of 400mW and 1.3W are common.

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Zener test characteristics.





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Uses of Zener Diodes

Since the voltage dropped across a Zener Diode is a knownand fixed value, Zener diodes are typically used to regulate thevoltage in electric circuits. Using a resistor to ensure that thecurrent passing through the Zener diode is at least 5mA (0.005

Amps), the circuit designer knows that the voltage drop across

the diode is exactly equal to the Zener voltage of the diode.

A zener diode can be used to make a

simple voltage regulation circuit as

shown. The output voltage is fixed at the

zener voltage of the zener diode used and

so can be used to power devices requiring

a fixed voltage.

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Zener terminal identificationand symbols.





d d

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Zener diodes.(Courtesy Siemens Corporation.)





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Light Emitting Diodes (LEDs)

Circuit symbol:

Function

LEDs emit light when an electric current passes

through them.

Connecting and soldering

LEDs must be connected the correct way round. The cathode is the

short lead and there may be a slight flat on the body of round LEDs.

If you can see inside the LED the cathode is the larger electrode (but

this is not an official identification method).

LEDs can be damaged by heat when soldering, but the risk is smallunless you are very slow. No special precautions are needed for

soldering most LEDs.

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Testing an LED

Never connect an LED directly to a battery or power

supply!

It will be destroyed almost instantly because too

much current will pass through and burn it out. LEDs must have a resistor in series to limit the current

to a safe value.

for quick testing purposes a 1k ohm resistor is

suitable for most LEDs if your supply voltage is 12V

or less. Remember to connect the LED the correct way!

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LED Displays

Dot matrix

Starburst

7-segment

Bargraph

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Hewlett-Packard subminiature high-efficiency red solid-state lamp:(a) appearance; (b) absolute maximum ratings; (c) electrical/optical characteristics.

(CourtesyHewlett-Packard Corporation.)





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diode symbols

DiodeZenerdiode

Schottkydiode

Tunneldiode

Light-emittingdiode Photodiode Varicap

Silicon

controlledrectifier

ch1a diode

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