pn junction / diode
DESCRIPTION
PN Junction / DIODE. Bollen. SEMICONDUCTOR Pure silicium P material boron doped N material stibium doped P material and N material PN junction PN junction layer 0V7 PN junction characteristic. DIODE characteristic DIODE DC and ac resistance DIODE load line DIODE flipped resistorline - PowerPoint PPT PresentationTRANSCRIPT
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PN Junction / DIODE
Bollen
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AGENDA
Bollen
SEMICONDUCTORPure siliciumP material boron dopedN material stibium dopedP material and N materialPN junctionPN junction layer 0V7PN junction characteristic
DIODE characteristicDIODE DC and ac resistanceDIODE load lineDIODE flipped resistorlineDIODE DC resistanceDIODE ac resistance
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Semiconductor, pure silicium
Bollen
Pure siliciumPure silicium
4 electrons4 electrons
Ideal is to have 8Ideal is to have 8
So share with your So share with your neighbourneighbour
Co-valence boundingCo-valence bounding
Electrical neutralElectrical neutral
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Semiconductor, pure silicium
Bollen
Pure siliciumPure silicium
4 electrons4 electrons
Ideal is to have 8Ideal is to have 8
So share with your neighbourSo share with your neighbour
Co-valence boundingCo-valence bounding
Electrical neutralElectrical neutral
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Semiconductor, P material boron doped
Bollen
P material = silicium P material = silicium (+4)(+4)
boron (+3) dopedboron (+3) doped
Boron misses Boron misses
1 positvie charge (positon) 1 positvie charge (positon) & &
1 negative charge 1 negative charge (electron)(electron)
Co-valence boundingCo-valence bounding
Electrical neutralElectrical neutral
P material misses one P material misses one electron, or has a place electron, or has a place for one electron, for one electron,
this is called a free this is called a free holehole
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Semiconductor, N material stibium doped
Bollen
N material = silicium N material = silicium (+4)(+4)
stibium (+5) dopedstibium (+5) doped
Stibium has got extra Stibium has got extra
1 positive charge (positon) 1 positive charge (positon) & &
1 negative charge 1 negative charge (electron)(electron)
Co-valence boundingCo-valence bounding
Electrical neutralElectrical neutral
N material has got one N material has got one extra electron out of the extra electron out of the bounding, bounding,
this is called a free this is called a free electronelectron
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P material and N material
Bollen
N material N material
= =
Free Free electronselectrons
P material P material = =
Free holesFree holes
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PN junction
Bollen
Anode = P=materialAnode = P=material
Kathode = N materialKathode = N material
KNAP = handsomeKNAP = handsome
K = NegativeK = Negative
A = PositiveA = Positive
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PN junction, depletion layer 0V7
Bollen
Depletion layer Depletion layer
can be made can be made
WiderWider by by
external reverse voltageexternal reverse voltage
SmallerSmaller by by
External froward voltageExternal froward voltage
Depletion layer; Uth = Depletion layer; Uth = 0V70V7
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PN junction, characteristic
Bollen
ForwardForward
Depletion layer is Depletion layer is gonegone
Ud > 0V7Ud > 0V7
Current can flowCurrent can flow
ReverseReverse
Depletion layer is widerDepletion layer is wider
Ud < 0V0Ud < 0V0
Current can NOT flowCurrent can NOT flow
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Diode, characteristic
Bollen
aa Diode Diode
Is aIs a
one one way way
streetstreet
forfor
currentcurrent
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Diode, characteristic
Bollen
AssumptionAssumption
TresholdTreshold
Voltage Voltage
for siliciumfor silicium
Ud = 0V7Ud = 0V7
for for germaniumgermanium
Ud = 0V2Ud = 0V2
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Diode, characteristic
Bollen
WhereWhere
id = diode currentid = diode current
Vd= diode voltageVd= diode voltage
KT/q = 26 mVKT/q = 26 mV
Iss = leakage current Iss = leakage current (1uA)(1uA)
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Diode, DC and ac resistance
Bollen
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Diode, Load line
Bollen
How to calculate the exact value of vd and id;How to calculate the exact value of vd and id;
Graphical; use load line, indicates the load of the Graphical; use load line, indicates the load of the diodediode
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Diode, Load line
Bollen
For shureFor shure
id = ir = iid = ir = i
For shureFor shure
vs = vd + vs = vd + vrvr
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Diode, Load line
Bollen
For shureFor shure For shureFor shure
id = ir = iid = ir = i vs = vd + vrvs = vd + vr
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Diode, Flipped resistor line
Bollen
Flip the resistor line and push the Flip the resistor line and push the twotwo
curves horizontally to fit; curves horizontally to fit; vs = vd + vs = vd + vrvr
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Diode, Load line
Bollen
The flippedThe flipped
resistor resistor lineline
is called is called
LOAD-LOAD-LINELINE
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Diode, DC resistance
Bollen
For DC resistance use For DC resistance use thethe
load line methodload line method
For large voltagesFor large voltages
normally normally Vd= 0V7Vd= 0V7 is is usedused
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Diode, ac resistance
Bollen
Differentiating givesDifferentiating gives
Rd = Rd = ΔΔvd/vd/ΔΔid = 26 mV / id = 26 mV / IdId
Where kT/q = 26 mVWhere kT/q = 26 mV