Bipolar Transistors - Voltage Amplifiers

Bipolar Transistors - Voltage Amplifiers

Bahan Kuliah Elektronika Dasar Pertemuan ke 11 FIELD EFFECT TRANSISTOR oleh Ir.Bambang Sutopo,M.Phil Jurusan Teknik Elektro FT-UGM 2007 1

DRIVER RELAY (diskusi tugas lalu) VCC VBE RB 2 I B JENUH IB-JENUH = arus basis yang membuat transistor dalam kondisi jenuh. DIODA

freewheel RELAY VCC RB Relay membutuhkan arus sekitar 50 sampai 100 mili Amper 2 TRANSISTOR SBG BUFER OP-AMP

Input 1 relay + Input 2 R _ R harus bisa membatasi arus agar arus yang dikeluarkan

op-amp tak terlalu besar. R harus masih dapat membuat transistor jenuh. 3 Pilihan R tergantung kemampuan IC relay mengeluarkan arus (source)

atau dimasuki arus (sink) R 25mA relay 100mA R

relay 200mA 4 Tegangan VCE vs Hambatan Basis 2500 Tegangan VCE (mV) 2000

Eka Ardi Daerah Tak stabil 1500 1000 500 0

1 10 2 10 3 10 RB (Ohm)

4 10 5 10 5 Arus Basis vs Hambatan Basis

90 80 Arus Basis (mA) 70 Eka Ardi 60 50 40

BC107 30 20 10 0 1 10 2

10 3 10 RB (Ohm) 4 10

5 10 6 Arus Basis (mA)/ Tegangan VCE (mV) 120 Arus Basis, Tegangan VCE dan Hambatan Basis

100 80 60 40 20 0 2

10 3 10 RB (Ohm) 4 10

7 45 Arus Basis, Tegangan VCE dan Hambatan Basis IB Arus Basis (mA)/ Tegangan VCE (mV) 40 35

1 30 25 2 20 3 15

VCE 10 5 0 100 200 300

400 500 600 RB (Ohm) 700 800

900 1000 8 LM 339/239 VCC Rpull-up Beban


+ _ 10 12V 4,7K + 8,2K

1K _ Lampu Vin 12V + 4,7K _

1K 11 12 IC 555 13 LM 741 14


17 SINK CURRENT 18 LM 124/234/324 19 IC 555 20


21 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. 22 Field Effect Transistor - FET Apakah 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 23ini berdasarkan transistor FET ini. FET vs BJT FET Gate (G) Drain(D)

Source(S) Gate Voltage Drain current Drain-source voltage BJT Base (B) Collector (C) Emitter (E) Base current Collector current

Collector-Emitter Voltage 24 Jenis-jenis FET JFET (Junction FET) MOSFET (Metal Oxide Silikon FET)

PMOS ( MOS saluran P) NMOS (MOS saluran N) Masih banyak lagi 25 ID FET VDS

FET Parameter FET : ID, VGS, VDS. VGS Dasar pemikiran FET: IS 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. 26 Junction FETs 27 JFET saluran N 28 aerah deplesi membesar dengan bertambahnya tegangan ba

29 30 Saluran N 31 32 33

34 Arus Drain current vs tegangan drain-ke-source (tegangan gate-source = 0) 35 n-Channel FET for vGS = 0. 36 Typical drain characteristics of an n-channel JFET. 37

If vDG exceeds the breakdown voltage VB, drain current increases rapidly. 38 39 KURVA KARAKTERISTIK Junction FET Hubungan VGS dan ID I D k VGS VP

k : konstanta VP : tegangan pinch-off atau threshold. Arus dibatasi hanya saat tegangan VGS = 0 40 2 Junction FET Sumber Arus

VDD RLoad RS 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. 41

KURVA VDS-ID Junction FET Linear Ada dua daerah operasi : Saturation saturation linear. Linear Saturation

2 I D k VGS VP 2 VDS I D 2k VGS VP VDS 2

42 JFET - variable resistor VDD RD VGS RG 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. VDS, DRAIN-SOURCE VOLTAGE, (Volts)

This makes it possible to have an element in a circuit that can be electronically adjusted. 43 JFET - variable resistor (2) VDD RD VGS

RG Now lets analyze the circuit. In the linear region we had a relationship between ID and VDS. 2 VDS I D 2k VGS VT VDS 2

To find the effective resistance this is the voltage across the channel divided by the current through the channel. 1 ID VDS

2k VGS VT RDS VDS 2 If it wasnt for the last term, we would have a value of 1/RDS that was proportional to VGS, the control voltage and didnt 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. 44

n-Channel depletion MOSFET. 45 n-Channel enhancement MOSFET showing channel length L and channel width W. 46 n-Channel depletion MOSFET showing channel length L and channel width W. 47 enhancement-mode n-channel MOSFET

48 vGS < Vto pn junction antara drain dan body reverse biased iD=0. 49 Terbentuk saluran N vGS < Vto pn junction antara drain dan body reverse biased iD=0.

50 For vGS < Vto the pn junction between drain and body is reverse biased and iD=0. 51 vGS >Vto terbentuk saluran n. vGS bertambah saluran membesar. vDS kecil ,I D sebanding dengan vDS. resistor tergantung nilai vGS. 52

vDS bertambah, saluran mengecil di drain dan Laju pertambahan iD : melambat Saat vDS> vGS -Vto, iD tetap 53 Threshold Voltage Vto (VP) 54

Kurva karakteristik transistor NMOS 55 Drain characteristics 56 Rangkaian penguat sederhana menggunakan NMOS . 57 Drain characteristics and load line 58

vDS versus time. 59 60 Graphical solution 61 62 The more nearly horizontal bias line results in less change in the Q-point.

63 Sinyal campuran 64 Rangkaian Ekivalen FET 65 Rangkaian ekivalen FET ( iD terpengaruh vDS) 66 Penentuan gm dan rd

67 Common-source amplifier. 68 Rangkaian Ekivalen Common-Source amplifier. 69 Common-source amplifier dengan nilai R 70

vo(t) dan vin(t) versus time 71 Gain magnitude versus frequency 72 Source follower. 73 Rangkaian Ekivalen Source Follower.

74 Common-gate amplifier. 75 n-Channel depletion MOSFET. 76 Drain current versus vGS in the saturation region for n-channel devices. 77

p-Channel FET circuit symbols. Sama = n-channel devices, kecuali arah panah 78 MOSFET-switch VDD RLOAD RG VGS

IRF510 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. 79 Note the log scale!

MOSFET-switch (2) Kurva ID vs. VGS. Ideal saklar: ON saat OFF Arus =0. Dari kuva terlihat : Tegangan VGS < 3 volt, ID = 0 OFF

>5V arus besar. 80 PMOS In this device the gate controls hole flow from source to drain. source

p It is made in n-type silicon. gate source drain p

n-type Si drain p n-type Si |VGS |>|Vt | + - p

P-MOS gate 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) 81

NMOS and PMOS Compared NMOS Body p-type Source n-type Drain n-type VGS positive VT positive

VDS positive ID positive (into drain) G S D ID n n p ID

B ID VGS=3V 1 mA (for IDS = 1mA) 2

3 4 VGS= 3V 1 mA (for IDS = -1mA)

VGS=0 1 PMOS Body n-type Source p-type Drain p-type VGS negative VT

negative VDS negative ID negative (into drain) G S D ID p n B

VGS=0 VDS 1 2 3 4


NMOS circuit symbol S PMOS circuit symbol A small circle is drawn at the gate to remind us that the polarities are reversed for PMOS. 83

PMOS Transistor Switch Model Operation compared to NMOS: It is complementary. VDD S G VDD


V=0 D Switch OPEN D Switch CLOSED D

For PMOS for the normal circuit connection is to connect S to VDD (The function of the device is a pull up) Switch is closed: Drain (D) is connected to Source (S) when VG =0 Switch is open : Drain (D) is disconnected from Source (S) when VG = VDD 84

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