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    EE201 Semiconductor DeviceEE201 Semiconductor Device 11

    TOPIC 2

    ~DIODES~

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    Doa mula kelasDoa mula kelas

    Ya Tuhan, lapangkanlah dadaku, mudahkanlahYa Tuhan, lapangkanlah dadaku, mudahkanlah

    segala urusanku, dan lepaskanlah kekakuan lidahku,segala urusanku, dan lepaskanlah kekakuan lidahku,

    agar mereka mengerti perkataanku.agar mereka mengerti perkataanku.(Thaha: 27)(Thaha: 27)

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    By the end of this class, studentsBy the end of this class, students

    should be able to:should be able to:~~ Understand the characteristics of diode and diode as a semiconductorUnderstand the characteristics of diode and diode as a semiconductor

    device.device.

    ~~ Determine !" characteristic curve for silicon diode and e#$lain:Determine !" characteristic curve for silicon diode and e#$lain:

    a. %nee "olta&e (Threshold volta&e )a. %nee "olta&e (Threshold volta&e )

    b. 'orard current (in milli m$ere scale)b. 'orard current (in milli m$ere scale)

    c. *everse current (in microm$ere scale)c. *everse current (in microm$ere scale)

    d. Brea+don volta&ed. Brea+don volta&e

    e. Burnin& level (hen d, "d e#ceeds ma#)e. Burnin& level (hen d, "d e#ceeds ma#)

    ~~ %no diode a$$lications as rectifiers.%no diode a$$lications as rectifiers.

    ~~ Diode as cli$$er and clam$er circuits.Diode as cli$$er and clam$er circuits.

    ~~ Understand other ty$es of diode:Understand other ty$es of diode:

    a. -ener diodea. -ener diode

    b. i&ht emittin& diode (/D)b. i&ht emittin& diode (/D)

    c. hotodiodec. hotodiode

    d. aser dioded. aser diode

    EE201-semiconductor deviceEE201-semiconductor device 33

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    DiodesDiodes

    ~~ n effect, diodes act li+e a fla$$er valven effect, diodes act li+e a fla$$er valve ote: this is the sim$lest $ossible model ofote: this is the sim$lest $ossible model of

    a diodea diode

    EE201 Semiconductor DeviceEE201 Semiconductor Device 55

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    DiodesDiodes

    ~ 'or the fla$$er valve, a small $ositive~ 'or the fla$$er valve, a small $ositive$ressure is reuired to o$en.$ressure is reuired to o$en.

    ~ i+eise, for a diode, a small $ositive~ i+eise, for a diode, a small $ositive

    volta&e is reuired to turn it on. Thisvolta&e is reuired to turn it on. This

    volta&e is li+e the volta&e reuired tovolta&e is li+e the volta&e reuired to

    $oer some electrical device. t is used u$$oer some electrical device. t is used u$

    turnin& the device on so the volta&es atturnin& the device on so the volta&es at

    the to ends of the diode ill differ.the to ends of the diode ill differ. The volta&e reuired to turn on a diode isThe volta&e reuired to turn on a diode is

    ty$ically around 8.9!8. volt for a standardty$ically around 8.9!8. volt for a standard

    silicon diode and a fe volts for a li&ht emittin&silicon diode and a fe volts for a li&ht emittin&

    diode (/D)diode (/D)EE201 Semiconductor DeviceEE201 Semiconductor Device 66

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    t the ;unction, free electrons from the !ty$e

    material fill holes from the !ty$e material. This

    creates an insulatin& layer in the middle of the

    diode called the de$letion

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    EE201 Semiconductor DeviceEE201 Semiconductor Device 88

    DIODE-FORWARD BIAS

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    EE201 Semiconductor DeviceEE201 Semiconductor Device99

    DIODE-REVERSE BIAS

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    Diode !" 5haracteristicDiode !" 5haracteristic~ 'or ideal diode, current flos only one ay~ 'or ideal diode, current flos only one ay

    ~ *eal diode is close to ideal~ *eal diode is close to ideal

    EE201 Semiconductor DeviceEE201 Semiconductor Device 1010

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    Diode !" 5haracteristicDiode !" 5haracteristic

    EE201 Semiconductor DeviceEE201 Semiconductor Device 1111

    'orard current'orard current == current flo hen forard bias volta&e arecurrent flo hen forard bias volta&e are&iven. (in milim$ere scale)&iven. (in milim$ere scale)

    *everse current*everse current ==small lea+a&e current, flo hen reverse biassmall lea+a&e current, flo hen reverse bias

    volta&e (in microm$ere scale (volta&e (in microm$ere scale (>>))))

    %nee "olta&e%nee "olta&e == threshold volta&e.(0i!8.7", ?e! [email protected]"). "olta&ethreshold volta&e.(0i!8.7", ?e! [email protected]"). "olta&e

    that current flo immediately.that current flo immediately.Brea+don volta&eBrea+don volta&e == volta&e that reverse current flo immediately.volta&e that reverse current flo immediately.

    ea+a&e 5urrentea+a&e 5urrent == Ahen a diode is reverse biased, a very smallAhen a diode is reverse biased, a very small

    amount of current can and does &o in reverseamount of current can and does &o in reverse directiondirection

    (i.e.o$$osite to conventional direction)(i.e.o$$osite to conventional direction) &ivin& rise to lea+a&e&ivin& rise to lea+a&e

    current.current.Burnin& evelBurnin& evel !! Ahen Ahen dd and "and "dd e#ceed ma#imum, thee#ceed ma#imum, the

    com$onents ill burn.com$onents ill burn.

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    deal Diodedeal Diode 'orard bias'orard bias= diode as a close sitch (3)= diode as a close sitch (3)

    because no resistance and volta&e dro$.because no resistance and volta&e dro$.

    *everse bias*everse bias== diode as o$en sitch (3''), infinitydiode as o$en sitch (3''), infinity

    resistance.resistance.

    EE201 Semiconductor DeviceEE201 Semiconductor Device 1212

    *everse bias

    3$en sitch (3'')

    5athodenode

    'orard bias

    5lose sitch (3)

    5athodenode

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    1313

    DIODE APPLICATIONSDIODE APPLICATIONS

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    2-1 Half-Wave Rectiers

    DIODEDIODE ability to conduct current in one direction andability to conduct current in one direction andbloc+ current in other direction bloc+ current in other direction

    used in circuit calledused in circuit called */5T'/* (ac dc)

    rectifierrectifieris an electrical device thatis an electrical device that

    converts alternatin& current (5), hichconverts alternatin& current (5), hich

    $eriodically reverses direction, to direct current$eriodically reverses direction, to direct current

    (D5), hich is in only one direction, a $rocess(D5), hich is in only one direction, a $rocess+non as+non as rectification.rectification.

    11

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    The basic function of a DC power supply isto convert an AC voltage to a constant DCvoltage (AC DC)

    Either half or full-wave

    rectier convert ac inputto a pulsating dc voltage.

    Eliminates the uctuations- produce smooth dc voltage

    Maintains a constavoltage

    The basic DC power supply

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    ~~ The a$$lied a.c si&nal across the secondary indin& chan&eThe a$$lied a.c si&nal across the secondary indin& chan&e

    $olarities after each half !cycle of su$$ly a.c volta&e.$olarities after each half !cycle of su$$ly a.c volta&e.

    ~~ t the time of the $ositive half!cycle of su$$ly a.c volta&e,t the time of the $ositive half!cycle of su$$ly a.c volta&e,

    diode is in forard biased and it conduct current in the circuits.diode is in forard biased and it conduct current in the circuits.

    ~~ t the time of ne&ative half!cycle of in$ut a.c volta&e, diodet the time of ne&ative half!cycle of in$ut a.c volta&e, diodebecomes reverse biased and it does not conduct current in thebecomes reverse biased and it does not conduct current in the

    circuits.circuits.

    ~~ n this ay, current flos via the load at the time of $ositiven this ay, current flos via the load at the time of $ositive

    half!cycle of in$ut a.c volta&e only here as no conduct currenthalf!cycle of in$ut a.c volta&e only here as no conduct current

    throu&h the load at the time of ne&ative half!cycle in the samethrou&h the load at the time of ne&ative half!cycle in the samedirection is obtain across load for other ne#t cycle.direction is obtain across load for other ne#t cycle.

    ~~ But this out$ut is $ulsatin& d.c .But this out$ut is $ulsatin& d.c .

    EE201 Semiconductor DeviceEE201 Semiconductor Device 1616

    Half-Wave Rectier

    Operation

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    1!1!

    A half wave

    rectier(ideal) allowsconduction for only180 or half of aco!plete cycle""

    During rst one cycle#

    Vingoes positive $diode FB$ conductcurrent

    Vin goes negative $diode RB $ no

    current% 0& The output fre'uencyis the sa!e as the input(sa!e shape)"

    The averaevalue !DC or

    !A!"#

    deal diode

    !odel

    p

    AVG

    VV =

    $$ %easure on &c volt'eter

    The Half-Wave Rectier

    ac source load resistor

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    ractical Diode barrier potential of 0"*& (+i) ta,en into account"

    During -ve half%cycle &in!ust overco!e &potentialfor forward bias"

    Example 1: Calculate the peak o/p voltage, VExample 1: Calculate the peak o/p voltage,