Kuliah Elektronika Dasar Minggu ke 4 DIODA

Kuliah Elektronika Dasar
Minggu ke 4
DIODA
Jurusan Teknik Elektro
Fakultas Teknik UGM
2007
1
FUNCTION
 Electrical ‘gate’

Current only flows one way
 Forward biased

Current flows
 Reverse biased

Blocks current
+
-
-
+
2
I-V characteristic
pn junction diode I-V characteristics
20
Forward Bias
15
Current
Breakdown Voltage
10
Reverse saturation current
0.7V Switch-on
5
0
-6
-5
-4
-3
-2
-1
0
1
2
3
4
Applied voltage
Reverse Bias
-5
-10
3
PN CONSTRUCTION
 Semiconductor material
 n-type

Excess electrons
 p-type

Excess holes
 ‘Join’ together



Depletion region
Redistribution of charge carriers
Contact potential
 0.7V
4
SAMBUNGAN PN
 p-type material
 n-type material
 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
5
FORWARD BIAS
 Applied voltage above
 Depletion region
0.7V
narrows as applied
voltage approaches 0.7V

depletion region is
removed

Depletion Region
V< 0.7V
charge carriers can flow
V> 0.7V
+
P
+
N
6
DAERAH DEPLESI MENYEMPIT  MENGHILANG
REVERSE BIAS
 Depletion region extends
 Higher voltage


Breakdown
Current flow
V< 0V
+
V<< 0V
DAERAH DEPLESI MELEBAR  MAKIN LEBAR
+
7
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.
8
PITA ENERGI SEBUAH ATOM
PITA HANTARAN
CELAH ENERGI
PITA VALENSI
INTI
9
PITA ENERGI
PITA
HANTARAN
No Gap
Large Gap
PITA VALENSI
Insulators
PITA
HANTARAN
PITA VALENSI
Metals
PITA
HANTARAN
Small Gap
PITA VALENSI
Semiconductors
10
Elektron di orbit terluar
Silicon
Boron
Phosphorus
Tetravalent
Trivalent
Pentavalent
“Acceptor”
“Donor”
11
PITA ENERGI
PITA HANTARAN
celah energi
PITA VALENSI
elektron
12
TERBENTUKNYA
HOLE
PITA HANTARAN
ELEKTRON BEBAS
ENERGI
TAMBAHAN
elektron
HOLE
PITA VALENSI
Jumlah Elektron Bebas = Jumlah Hole
13
P-N JUNCTION FORMATION
p-type material
n-type material
Semiconductor material
doped with acceptors.
Semiconductor material
doped with donors.
Material has high hole
concentration
Material has high
concentration of free
electrons.
Concentration of free
electrons in p-type material
is very low.
Concentration of holes in
n-type material is very low.
14
P-N JUNCTION FORMATION
p-type material
n-type material
Contains
NEGATIVELY
charged acceptors
(immovable) and
POSITIVELY charged
holes (free).
Contains POSITIVELY
charged donors
(immovable) and
NEGATIVELY
charged free electrons.
Total charge = 0
Total charge = 0
15
P-N JUNCTION FORMATION
What happens if n- and p-type materials are in close contact?
p-type material
n-type material
Contains
NEGATIVELY
charged acceptors
(immovable) and
POSITIVELY charged
holes (free).
Contains POSITIVELY
charged donors
(immovable) and
NEGATIVELY
charged free electrons.
Total charge = 0
Total charge = 0
16
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)
17
p- n junction formation
What happens if n- and p-type materials are in close contact?
p-type
n-type
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.
18
p- n junction current – voltage characteristics
What happens when the voltage is applied to a p-n junction?
p-type
n-type
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
19
p- n junction current – voltage characteristics
What happens if voltage of opposite polarity is applied to a p-n junction?
p-type
n-type
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
When the voltage exceeds the built-in voltage, the current can flow through
20
the p-n junction
Diode current – voltage (I-V) characteristics
Semiconductor diode consists of a p-n junction with two
contacts attached to the p- and n- sides
p
n
V
0

 qV  
I  I S exp 
  1
 kT  

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).
When the voltage V is positive (“forward” polarity) the exponential term
increases rapidly with V and the current is high.
21
Δίοδος
22
p-n junction formation
p-type material
n-type material
Semiconductor material
doped with acceptors.
Semiconductor material
doped with donors.
Material has high hole
concentration
Material has high
concentration of free
electrons.
Concentration of free
electrons in p-type material
is very low.
Concentration of holes in
n-type material is very low.
23
IKATAN KOVALENT
24
SILIKON DIPANASI
25
DI DOPING ATOM BERVALENSI 5
BAHAN
N
ION POS
26
DI DOPING ATOM BERVALENSI 3
BAHAN
P
ION NEG
27
DI DOPING ATOM BERVALENSI 5
BAHAN
N
ION POS
28
DI DOPING ATOM BERVALENSI 3
BAHAN
P
ION NEG
29
BAGAIMANA MEMBUAT BAHAN N ?
 Bahan silikon diberi doping atom bervalensi 5

(misal : pospor)
Uap pospor
Si
RUANG HAMPA
Atom pospor disebut DONOR
N
30
Bahan semikonduktor jenis P
 Bahan silikon diberi doping atom bervalensi 3

(misal : boron)
Uap boron
Si
RUANG HAMPA
Atom boron disebut ASEPTOR
P
31
DISTRIBUSI HOLE
32
TEGANGAN KONTAK
33
Simbul dioda dan arah arus
Karakteristik ideal
Rangkaian ekivalen saat reverse bias
Rangkaian ekivalen saat forward bias
34
PENDEKATAN IDEAL
35
p- n diode applications:
current rectifiers
 qV

I  I S exp 
 1
 kT

+
-
+
-
IS
Voltage
Current
Time
Time
36
PENYEARAH
setengah gelombang
Tegangan input
Saat forward
0
Saat reverse
π
2π
Tegangan output
37
TEGANGAN DC RATA-RATA
 Mengintegralkan
VDC
satu periode
2
2π
VDC
Vm
Vm
  1  1 

2

1
VDC 
Vm sin  d

2 0
2
Vm
VDC 
sin  d

2 0
VDC
Vm

  cos  0
2
38
Bila ada tegangan lawan
39
Contoh rangkaian dioda
40
MELIHAT DETIL
41
PENGARUH PANAS
42
GARIS KERJA (load line)
43
44
MODEL DIODA DENGAN rD
45
DIODA TANPA rD
46
DIODA TANPA rD
47
1
2
3
48
POWER SUPPLY
CATU DAYA
49
50
PENYEARAH
GELOMBANG PENUH
51
TRAFO TANPA CENTER TAP
(PENYEARAH BRIDGE)
52
FILTER C
53
PENGARUH BEBAN RL
54
RIPLE (RIAK)
55
SUPERDIODA (PENYEARAH PRESISI)
56
CLIPPER (PEMANGKAS)
Vin
D1
L+
D2
Vout
L-
Vin : tegangan sinus
57
PR
Vin adalah tegangan kotak ± 10 Volt
58
PENGGESER DAN PENGARUH R
59
PENGGANDA TEGANGAN
TEGANGAN PADA D1
60
PENGHASIL TEGANGAN GANDA
(DUAL SUPPLY)
61