1 Kuliah Elektronika Dasar Minggu ke 4 DIODA Jurusan Teknik Elektro Fakultas Teknik UGM 2007
Jan 13, 2016
1
Kuliah Elektronika Dasar Minggu ke 4
DIODA
Jurusan Teknik ElektroFakultas Teknik UGM
2007
2
FUNCTION
Electrical ‘gate’ Current only flows one way
Forward biased Current flows
Reverse biased Blocks current
+ -
- +
3
pn junction diode I-V characteristics
-10
-5
0
5
10
15
20
-6 -5 -4 -3 -2 -1 0 1 2 3 4
Applied voltageC
urr
en
t
I-V characteristic
Forward Bias
Reverse Bias
Breakdown Voltage
Reverse saturation current 0.7V Switch-on
4
PN CONSTRUCTION
Semiconductor material n-type
Excess electrons
p-type Excess holes
‘Join’ together Depletion region Redistribution of charge carriers Contact potential
0.7V
5
p-type material n-type material
SAMBUNGAN PN
Holes diffuse into the n-type and ‘swallow’ electrons
Electrons diffuse into the p-type and ‘fill holes’
Depletion region formed
No free charge carriers 0.7V contact potential
6
FORWARD BIAS
Applied voltage above 0.7V depletion region is
removed charge carriers can flow
V< 0.7V V> 0.7V
P N
+ +
Depletion region narrows as applied voltage approaches 0.7V
Depletion Region
DAERAH DEPLESI MENYEMPIT MENGHILANG
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REVERSE BIAS
Depletion region extendsHigher voltage
Breakdown Current flow
V< 0V V<< 0V+ +
DAERAH DEPLESI MELEBAR MAKIN LEBAR
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Bohr model(I hope it’s not bohring)
The Bohr model is a planetary model, where the electron orbits the nucleus like a planet orbits the Sun.
An electron is only allowed in DISCRETE orbits (n=1, n=2, n=3, etc.)
The higher the orbit, the higher the energy of the electron.
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PITA ENERGI SEBUAH ATOM
PITA HANTARAN
PITA VALENSI
CELAH ENERGI
INTI
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PITA ENERGI
PITA HANTARAN
PITA VALENSI
PITA HANTARAN
PITA VALENSI PITA VALENSI
PITA HANTARAN Large Gap
No Gap
Small Gap
Semiconductors Metals Insulators
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Elektron di orbit terluar
SiliconTetravalent
BoronTrivalent
“Acceptor”
PhosphorusPentavalent
“Donor”
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PITA ENERGI
PITA HANTARAN
PITA VALENSIelektron
celah energi
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TERBENTUKNYA HOLE
elektron
PITA HANTARAN
ELEKTRON BEBAS
HOLE
ENERGI
TAMBAHAN
Jumlah Elektron Bebas = Jumlah Hole
PITA VALENSI
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p-type material
Semiconductor material doped with acceptors.
Material has high hole concentration
Concentration of free electrons in p-type material is very low.
n-type material
Semiconductor material doped with donors.
Material has high concentration of free electrons.
Concentration of holes in n-type material is very low.
P-N JUNCTION FORMATION
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P-N JUNCTION FORMATION
p-type material
Contains NEGATIVELY charged acceptors (immovable) and POSITIVELY charged holes (free).
Total charge = 0
n-type material
Contains POSITIVELY charged donors (immovable) and NEGATIVELY charged free electrons.
Total charge = 0
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p-type material
Contains NEGATIVELY charged acceptors (immovable) and POSITIVELY charged holes (free).
Total charge = 0
n-type material
Contains POSITIVELY charged donors (immovable) and NEGATIVELY charged free electrons.
Total charge = 0
What happens if n- and p-type materials are in close contact?
P-N JUNCTION FORMATION
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p- n junction formation
What happens if n- and p-type materials are in close contact?
Being free particles, electrons start diffusing from n-type material into p-material
Being free particles, holes, too, start diffusing from p-type material into n-material
Have they been NEUTRAL particles, eventually all the free electrons and holes had uniformly distributed over the entire compound crystal.
However, every electrons transfers a negative charge (-q) onto the p-side and also leaves an uncompensated (+q) charge of the donor on the n-side. Every hole creates one positive charge (q) on the n-side and (-q) on the p-side
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p- n junction formation
What happens if n- and p-type materials are in close contact?
Electrons and holes remain staying close to the p-n junction because negative and positive charges attract each other.
Negative charge stops electrons from further diffusion
Positive charge stops holes from further diffusion
The diffusion forms a dipole charge layer at the p-n junction interface.
There is a “built-in” VOLTAGE at the p-n junction interface that prevents penetration of electrons into the p-side and holes into the n-side.
p-type n-type
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p- n junction current – voltage characteristicsWhat happens when the voltage is applied to a p-n junction?
The polarity shown, attracts holes to the left and electrons to the right.
According to the current continuity law, the current can only flow if all the charged particles move forming a closed loop
However, there are very few holes in n-type material and there are very few electrons in the p-type material. There are very few carriers available to support the current through the junction plane
For the voltage polarity shown, the current is nearly zero
p-type n-type
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p- n junction current – voltage characteristics
What happens if voltage of opposite polarity is applied to a p-n junction?
The polarity shown, attracts electrons to the left and holes to the right.
There are plenty of electrons in the n-type material and plenty of holes in the p-type material.
There are a lot of carriers available to cross the junction.
When the voltage applied is lower than the built-in voltage, the current is still nearly zero
p-type n-type
When the voltage exceeds the built-in voltage, the current can flow through the p-n junction
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Diode current – voltage (I-V) characteristics
1
kT
qVII S exp
p n
Semiconductor diode consists of a p-n junction with two contacts attached to the p- and n- sides
IS is usually a very small current, IS ≈ 10-17 …10-13 A
When the voltage V is negative (“reverse” polarity) the exponential term ≈ -1; The diode current is ≈ IS ( very small).
0 V
When the voltage V is positive (“forward” polarity) the exponential term increases rapidly with V and the current is high.
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Δίοδος
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p-type material
Semiconductor material doped with acceptors.
Material has high hole concentration
Concentration of free electrons in p-type material is very low.
n-type material
Semiconductor material doped with donors.
Material has high concentration of free electrons.
Concentration of holes in n-type material is very low.
p-n junction formation
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IKATAN KOVALENT
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SILIKON DIPANASI
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DI DOPING ATOM BERVALENSI 5
ION POS
BAHAN N
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DI DOPING ATOM BERVALENSI 3
BAHAN P
ION NEG
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DI DOPING ATOM BERVALENSI 5
ION POS
BAHAN N
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DI DOPING ATOM BERVALENSI 3
BAHAN P
ION NEG
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BAGAIMANA MEMBUAT BAHAN N ?
Bahan silikon diberi doping atom bervalensi 5 (misal : pospor)
Uap pospor
Si N
Atom pospor disebut DONOR
RUANG HAMPA
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Bahan semikonduktor jenis P
Bahan silikon diberi doping atom bervalensi 3 (misal : boron)
Uap boron
Si P
Atom boron disebut ASEPTOR
RUANG HAMPA
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DISTRIBUSI HOLE
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TEGANGAN KONTAK
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Simbul dioda dan arah arus
Karakteristik ideal
Rangkaian ekivalen saat reverse bias Rangkaian ekivalen saat forward bias
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PENDEKATAN IDEAL
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p- n diode applications:current rectifiers
1exp
kT
qVII S
IS
1exp
kT
qVII S
IS
+-
Time
Voltage+-
Time
Current
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PENYEARAH setengah gelombang
Saat forward
Saat reverse
Tegangan input
Tegangan output
0 π 2π
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TEGANGAN DC RATA-RATA
Mengintegralkan satu periode
2
0
sin2
1dVV mDC
2
0
sin2
dV
V mDC
0cos
2 m
DC
VV
mmDC
VVV 11
2
2π
VDC
39
Bila ada tegangan lawan
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Contoh rangkaian dioda
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MELIHAT DETIL
42
PENGARUH PANAS
43
GARIS KERJA (load line)
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45
MODEL DIODA DENGAN rD
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DIODA TANPA rD
47
DIODA TANPA rD
48
1 2 3
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POWER SUPPLYCATU DAYA
50
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PENYEARAH GELOMBANG PENUH
52
TRAFO TANPA CENTER TAP(PENYEARAH BRIDGE)
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FILTER C
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PENGARUH BEBAN RL
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RIPLE (RIAK)
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SUPERDIODA (PENYEARAH PRESISI)
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CLIPPER (PEMANGKAS)
Vin : tegangan sinus
VoutVinD1 D2L+ L-
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PR
Vin adalah tegangan kotak ± 10 Volt
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PENGGESER DAN PENGARUH R
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PENGGANDA TEGANGAN
TEGANGAN PADA D1
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PENGHASIL TEGANGAN GANDA(DUAL SUPPLY)