FIELD EFFECT TRANSISTOR
-
Upload
jemima-young -
Category
Documents
-
view
128 -
download
4
description
Transcript of FIELD EFFECT TRANSISTOR
1
FIELD EFFECT TRANSISTOR
olehIr.Bambang Sutopo,M.Phil
Jurusan Teknik ElektroFT-UGM
2007
Bahan Kuliah
Elektronika DasarPertemuan ke 11
2
DRIVER RELAY(diskusi tugas lalu)
VVCC
RELAYDIODADIODAfreewheelfreewheel
Relay membutuhkan arus sekitar 50 sampai 100 mili Amper
RB
JENUHB
BECCB I
VVR
2
IB-JENUH = arus basis yang membuat transistor dalam kondisi jenuh.
3
TRANSISTOR SBG BUFER OP-AMP
+
_
Input 1
Input 2
relay
R
R harus bisa membatasi arus agar arus yang dikeluarkan op-amp tak terlalu besar.
R harus masih dapat membuat transistor jenuh.
4
Pilihan R tergantung
kemampuan IC mengeluarkan arus
(source)atau
dimasuki arus(sink)
relay
relay
relay
200mA
100mA R
25mA
R
5101
102
103
104
105
0
500
1000
1500
2000
2500Tegangan VCE vs Hambatan Basis
RB (Ohm)
Teg
anga
n V
CE
(m
V) Eka Ardi
Daerah Tak stabil
6101
102
103
104
105
0
10
20
30
40
50
60
70
80
90Arus Basis vs Hambatan Basis
RB (Ohm)
Aru
s B
asis
(m
A) Eka Ardi
BC107
710
210
310
40
20
40
60
80
100
120Arus Basis, Tegangan VCE dan Hambatan Basis
RB (Ohm)
Aru
s B
asis
(m
A)/
Teg
anga
n V
CE
(m
V)
8100 200 300 400 500 600 700 800 900 10000
5
10
15
20
25
30
35
40
45Arus Basis, Tegangan VCE dan Hambatan Basis
RB (Ohm)
Aru
s B
asis
(m
A)/
Teg
anga
n V
CE
(m
V)
1
2
3
IB
VCE
9
LM 339/239
OPEN
COLLECTOR
VCC
Beban
Rpull-up
10
AND
+
_
+
_
12V
1K
11
+
_
+
_
12V
1K
4,7K
4,7K
8,2K
12V
1K
Vin
Lampu
12
13
IC 555
14
LM 741
15
LM 358
16
TOTEM POLE OUTPUT
LM 358
17
SOURCE CURRENT
18
SINK CURRENT
19
LM 124/234/324
20
IC 555
21
relay
RDIODA FOTO
KOMPARATOR SCHMITT
PROYEK KITA
22
Field Effect Transistor - FET
Mengapa kita masih perlu transistor jenis lain?
BJT mempunyai sedikit masalah.
BJT selalu memerlukan arus basis IB, walaupun arus ini kecil, tetapi tidak bisa diabaikan, terutama sekali saat BJT digunakan sebagai saklar, pasti dibutuhkan arus yang cukup besar untk membuat transistor jenuh.
23
Field Effect Transistor - FETApakah ada jenis transistor lain yang bisa digerakkan dengan tegangan tanpa membutuhkan arus ?
Jawabannya ada di FET.
Dengan perantaraan FET, kita dapat menghubungkan peralatan komputer atau transduser yang tidak bisa menghasilkan arus, dengan alat yang lebih besar.
FET bisa digunakan sbg bufer, sehingga tidak membutuhkan arus dari komputer/trasduser.
Teknologi modern pembuatan IC, ternyata dimensi transistor FET bisa dibuat sangat kecil, sehingga pembuatan IC saat ini berdasarkan transistor FET ini.
24
FET vs BJT
BJTBase (B)Collector (C)Emitter (E)
Base currentCollector currentCollector-Emitter Voltage
FETGate (G)
Drain(D)
Source(S)
Gate VoltageDrain currentDrain-source voltage
25
Jenis-jenis FET
• JFET (Junction FET)
• MOSFET (Metal Oxide Silikon FET)
• PMOS ( MOS saluran P)
• NMOS (MOS saluran N)• Masih banyak lagi
26
FETFET VDS
VGS
ID
IS
Parameter FET : ID, VGS, VDS.
Dasar pemikiran FET:
Ada arus ID = IS yang mengalir melalui saluran, yang besarnya saluran dikendalikan oleh tegangan VGS.
Karena arus lewat saluran (yang berupa hambatan) maka ada tegangan VDS.
27
Junction FETs
28
JFET saluran N
29
Daerah deplesi membesar dengan bertambahnya tegangan balik
30
31
Saluran N
32
33
34
35
Arus Drain current vs tegangan drain-ke-source (tegangan gate-source = 0)
36
n-Channel FET for vGS = 0.
37
Typical drain characteristics of an n-channel JFET.
38
If vDG exceeds the breakdown voltage VB, drain current increases rapidly.
39
40
KURVA KARAKTERISTIK Junction FET
Hubungan
VGS dan ID
2PGSD VVkI
k : konstanta
VP : tegangan pinch-off atau threshold.
Arus dibatasi hanya saat tegangan VGS = 0
41
Junction FET – Sumber Arus
Kurva tak dipengaruhi tegangan VDS.
Arus hanya dipengaruhi VGS bukan VDS.
RS membuat VGS selalu negatip.
Misalnya RS = 4K, VGS = -4 V.
Arus di Rload = 1 mA.
RS
VDD
RLoad
42
KURVA VDS-ID Junction FET
22
2DS
DSPGSD
VVVVkI
Ada dua daerah operasi :
saturation
linear.
Linear 2PGSD VVkI
SaturationLinear
Saturation
43
For low values of VDS the slopes, change from
a resistance (~5v/2.7mA~1.9k) to
a resistance (5v/10mA~0.5k).
A resistance is controlled by an input voltage.
VGS
RG
VDD
RD
VDS, DRAIN-SOURCE VOLTAGE, (Volts)
This makes it possible to have an element in a circuit that can be electronically adjusted.
JFET - variable resistor
44
JFET - variable resistor (2)
Now lets analyze the circuit. In the linear region we had a relationship between ID and VDS.
To find the effective resistance this is the voltage across the channel divided by the current through the channel.
22
2DS
DSTGSD
VVVVkI
VGS
RG
VDD
RD
22
1 DSTGS
DS
D
DS
VVVk
V
I
R
If it wasn’t for the last term, we would have a value of 1/RDS that was proportional to VGS, the control voltage and didn’t depend on VDS (remember VT is a constant of the FET, the pinch off voltage). This is like a resistor, and it forms a VOLTAGE DIVIDER with RD.
45
n-Channel depletion MOSFET.
46
n-Channel enhancement MOSFET showing channel length L and channel width W.
47
n-Channel depletion MOSFET showing channel length L and channel width W.
48
enhancement-mode n-channel MOSFET
49
vGS < Vto pn junction antara drain dan body reverse biased iD=0.
50
vGS < Vto pn junction antara drain dan body reverse biased iD=0.
Terbentuk saluran N
51
For vGS < Vto the pn junction between drain and body is reverse biased and iD=0.
52
vGS >Vto terbentuk saluran n. vGS bertambah saluran membesar.
vDS kecil ,I D sebanding dengan vDS.
resistor tergantung nilai vGS.
53
vDS bertambah, saluran mengecil di drain dan Laju pertambahan iD : melambat
Saat vDS> vGS -Vto, iD tetap
54
Threshold VoltageVto (VP)
55
Kurva karakteristik transistor NMOS
56Drain characteristics
57
Rangkaian penguat sederhana menggunakan NMOS .
58Drain characteristics and load line
59
vDS versus time.
60
61Graphical solution
62
63
The more nearly horizontal bias line results in less change in the Q-point.
64
Sinyal campuran
65
Rangkaian Ekivalen FET
66
Rangkaian ekivalen FET ( iD terpengaruh vDS)
67Penentuan gm dan rd
68
Common-source amplifier.
69
Rangkaian Ekivalen Common-Source amplifier.
70Common-source amplifier dengan nilai R
71 vo(t) dan vin(t) versus time
72
Gain magnitude versus frequency
73
Source follower.
74
Rangkaian Ekivalen Source Follower.
75
Common-gate amplifier.
76
n-Channel depletion MOSFET.
77
Drain current versus vGS in the saturation region for n-channel devices.
78
p-Channel FET circuit symbols. Sama = n-channel devices,
kecuali arah panah
79
MOSFET-switch
Power MOSFET dapat dialiri arus besar sampai 75 A, dan daya 150 W.
Saat ON punya hambatan sekitar 10 Ohm.
Contoh : IRF510
Mempunyai arus maksimum 5,6 A dab hambatan saat ON 0,4 Ohm.
IRF510
VGS
RG
VDD
RLOAD
80
MOSFET-switch (2)
Kurva ID vs. VGS.
Ideal saklar:
saat OFF Arus =0.
Dari kuva terlihat :
Tegangan VGS
< 3 volt, ID = 0
> 5 V arus besar. OFF
ON
Note the log scale!
81
PMOS
It is made in n-type silicon.
In this device the gate controls hole flow from source to drain.
source
drain
n-type Si p
gate
+ -
p
What if we apply a big negative voltage on the gate?
If |VGS |>|Vt | (both negative)
then we induce a + charge on the surface (holes)
source drain
n-type Si
P-MOSgate
p p
|VGS |>|Vt |
82
NMOS and PMOS Compared NMOS“Body” – p-typeSource – n-typeDrain – n-type VGS – positive
VT – positive
VDS – positive
ID – positive (into drain)
PMOS“Body” – n-typeSource – p-typeDrain – p-type VGS – negative
VT – negative
VDS – negative
ID – negative (into drain)G
n nID
DS
p
B
G
pID
DS
nB
ID
4321VDS
VGS=3V1 mA
VGS=0
(for IDS = 1mA)
4321VDS
VGS= 3V1 mA
VGS=0
ID
(for IDS = -1mA)
83
NMOS circuit symbol
CIRCUIT SYMBOLS
G
S
D
A small circle is drawn at the gate to remind us that the polarities are reversed for PMOS.
PMOS circuit symbol
G
S
D
84
PMOS Transistor Switch Model
Operation compared to NMOS: It is complementary.
For PMOS for the normal circuit connection is to connect S to VDD (The function of the device is a “pull up”)
VG = VDD
Switch is open : Drain (D) is disconnected from Source (S) when VG = VDD
VG =0
Switch is closed: Drain (D) is connected to Source (S) when VG =0
G
S
D
VDD
VDD
Switch OPEN
VDD
G
S
D
V=0
Switch CLOSED
S
D
G