BB

CC

EE

BJT – Bipolar Junction TransistorBJT – Bipolar Junction Transistor

Dua Type BJT Transistor:Dua Type BJT Transistor:

npnnpn pnppnp

nn pp nnEE

BB

CC pp nn ppEE

BB

CC

Cross SectionCross Section Cross SectionCross Section

BB

CC

EESymbolSymbol

BB

CC

EE

SymbolSymbol

• Collector doping is usually ~ 10Collector doping is usually ~ 1066

• Base doping is slightly higher ~ 10Base doping is slightly higher ~ 1077 – 10 – 1088

• Emitter doping is much higher ~ 10Emitter doping is much higher ~ 101515

Rumusan Dasar BJTRumusan Dasar BJT

BB

CCEEIIEE IICC

IIBB

--

++VVBEBE VVBCBC

++

--

++-- VVCECE

BB

CCEEIIEE IICC

IIBB--

++VVEBEB VVCBCB

++

--

++ --VVECEC

npnnpnIIEE = I = IBB + I + ICC

VVCECE = -V = -VBCBC + V + VBEBE

pnppnpIIEE = I = IBB + I + ICC

VVECEC = V = VEBEB - V - VCBCB

DC DC and DC and DC

= Arus penguatan Common-emitter = Arus penguatan Common-emitter

= Arus penguatan Common-base= Arus penguatan Common-base

= I= ICC = I = ICC

IIBB I IEE

Hubungan antara dua parameters tersebut adalah:Hubungan antara dua parameters tersebut adalah:

= = = =

+ 1+ 1 1 - 1 -

BJT ExampleBJT ExampleKonfigurasi Common-Base Transistor NPNKonfigurasi Common-Base Transistor NPN

++__

++__

Diketahui : IDiketahui : IBB = 50 = 50 A , I A , ICC = 1 mA = 1 mA

Hitung : IHitung : IEE , , , and , and

Penyelesaian:Penyelesaian:

IIEE = I = IBB + I + ICC = 0.05 mA + 1 mA = 1.05 mA = 0.05 mA + 1 mA = 1.05 mA

= I= ICC / I / IBB = 1 mA / 0.05 mA = 20 = 1 mA / 0.05 mA = 20

= I= ICC / I / IEE = 1 mA / 1.05 mA = 0.95238 = 1 mA / 1.05 mA = 0.95238

Juga dapat dicari dengan Juga dapat dicari dengan dengan rumus dengan rumus sebagai berikut.sebagai berikut.

= = = 20 = 0.95238 = 20 = 0.95238 + 1 21+ 1 21

IICC

IIEE

IIBB

VVCBCB

VVBEBE

EE

CC

BB

Curve TransconductanceCurve Transconductance BJT BJT Transistor Tipe NPN Transistor Tipe NPN

VVBEBE

IICC

2 mA2 mA

4 mA4 mA

6 mA6 mA

8 mA8 mA

0.7 V0.7 V

Arus Collector :Arus Collector :

IICC = = I IESES eeVVBEBE//VVTT

Transconductance: Transconductance: (slope of the curve)(slope of the curve)

ggmm = = I ICC / / V VBEBE

IIESES = Arus saturasi terbalik dari = Arus saturasi terbalik dari B-E Junction.B-E Junction.

VVTT = kT/q = 26 mV (@ T=300K) = kT/q = 26 mV (@ T=300K)

= Coefisien emisi= Coefisien emisi

biasanya ~1biasanya ~1

Modes of OperationModes of Operation

• Posisi terbaik pada daerah operasiPosisi terbaik pada daerah operasi

• Beroperasi sebagai penguatBeroperasi sebagai penguatActive:Active:

Saturation:Saturation: • Transistor berada sebagaimana pada posisi short Transistor berada sebagaimana pada posisi short circuit.circuit.

Cutoff:Cutoff: • Arus transistor nolArus transistor nol

• Transistor yang edial sebagaimana posisi saklar Transistor yang edial sebagaimana posisi saklar terbukaterbuka

* Note: There is also a mode of operation * Note: There is also a mode of operation called inverse active, but it is rarely used.called inverse active, but it is rarely used.

TigaTypes dari Bias BJTTigaTypes dari Bias BJT

Bias transistor adalah kondisi tegangan dimana transistor Bias transistor adalah kondisi tegangan dimana transistor tersebut bisa melakukan operasi (kerja).tersebut bisa melakukan operasi (kerja).

Bias Common-Base (CB) :Bias Common-Base (CB) : input input = V= VEBEB & I & IEE

output = Voutput = VCBCB & I & ICC

Bias Common-Emitter (CE):Bias Common-Emitter (CE): input input = V= VBEBE & I & IBB

outputoutput = V= VCECE & I & ICC

Bias Common-Collector (CC):Bias Common-Collector (CC): input input = V= VBCBC & I & IBB

output output = V= VECEC & I & IEE

Common-BaseCommon-BaseAlthough the Common-Base configuration is not the most Although the Common-Base configuration is not the most

common biasing type, it is often helpful in the understanding of common biasing type, it is often helpful in the understanding of how the BJT works. how the BJT works.

Emitter-Current CurvesEmitter-Current Curves

Satu

ratio

n R

egio

nSa

tura

tion

Reg

ion

IIEE

IICC

VVCBCB

Active Active RegionRegion

CutoffCutoffIIEE = 0 = 0

Common-BaseCommon-BaseCircuit Diagram: NPN TransistorCircuit Diagram: NPN Transistor

++ __ ++ __

IICC IIEE

IIBB

VVCBCB VVBEBE

EECC

BB

VVCECE

VVBEBEVVCBCB

Region of Region of OperationOperation IICC VVCECE VVBEBE VVCBCB

C-B C-B BiasBias

E-B E-B BiasBias

ActiveActive IIBB =V=VBEBE+V+VCECE ~0.7V~0.7V 0V0V Rev.Rev. Fwd.Fwd.

SaturationSaturation MaxMax ~0V~0V ~0.7V~0.7V -0.7V<V-0.7V<VCECE<0<0 Fwd.Fwd. Fwd.Fwd.

CutoffCutoff ~0~0 =V=VBEBE+V+VCECE 0V0V 0V0V Rev.Rev. NoneNone/Rev./Rev.

The Table Below lists assumptions The Table Below lists assumptions that can be made for the attributes that can be made for the attributes of the common-base biased circuit of the common-base biased circuit in the different regions of in the different regions of operation. Given for a Silicon NPN operation. Given for a Silicon NPN transistor.transistor.

Common-EmitterCommon-EmitterCircuit DiagramCircuit Diagram

++__

VVCCCC

IICCVVCECE

IIBB

Collector-Current CurvesCollector-Current Curves

VVCECE

IICC

Active Active RegionRegion

IIBB

Saturation RegionSaturation RegionCutoff RegionCutoff Region

IIBB = 0 = 0

Region of Operation

Description

Active Arus basis yang kecil mengontrol arus colektor yang besar

Saturation VCE(sat) ~ 0.2V, VCE increases with IC

Cutoff Pada kondisi IB mendekati 0, edialnya, IC juga sama dengan 0.

Common-CollectorCommon-Collector

Emitter-Current CurvesEmitter-Current Curves

VVCECE

IIEE

Active Active RegionRegion

IIBB

Saturation RegionSaturation RegionCutoff RegionCutoff Region

IIBB = 0 = 0

The Common-The Common-Collector biasing Collector biasing circuit is basically circuit is basically equivalent to the equivalent to the common-emitter common-emitter biased circuit except biased circuit except instead of looking at instead of looking at IICC as a function of V as a function of VCECE and Iand IB B we are looking we are looking at Iat IEE..

Also, since Also, since ~ 1, and ~ 1, and = I = ICC/I/IEE that means that means IICC~I~IEE

Eber-Moll BJT ModelEber-Moll BJT ModelThe Eber-Moll Model for BJTs is fairly complex, but it is The Eber-Moll Model for BJTs is fairly complex, but it is

valid in all regions of BJT operation. The circuit diagram valid in all regions of BJT operation. The circuit diagram below shows all the components of the Eber-Moll Model:below shows all the components of the Eber-Moll Model:

EE CC

BB

IIRRIIFF

IIEE IICC

IIBB

RRIIEERRIICC

Eber-Moll BJT ModelEber-Moll BJT Model

RR = Common-base current gain (in forward active mode) = Common-base current gain (in forward active mode)

FF = Common-base current gain (in inverse active mode) = Common-base current gain (in inverse active mode)

IIESES = Reverse-Saturation Current of B-E Junction = Reverse-Saturation Current of B-E Junction

IICSCS = Reverse-Saturation Current of B-C Junction = Reverse-Saturation Current of B-C Junction

IICC = = FFIIFF – I – IRR IIBB = I = IEE - I - ICC

IIEE = I = IFF - - RRIIRR

IIFF = I = IESES [exp(qV [exp(qVBEBE/kT) – 1]/kT) – 1] IIRR = I = ICC [exp(qV [exp(qVBCBC/kT) – 1]/kT) – 1]

If IIf IESES & I & ICSCS are not given, they can be determined using various are not given, they can be determined using various BJT parameters.BJT parameters.

Small Signal BJT Equivalent CircuitSmall Signal BJT Equivalent CircuitThe small-signal model can be used when the BJT is in the active region. The small-signal model can be used when the BJT is in the active region.

The small-signal active-region model for a CB circuit is shown below:The small-signal active-region model for a CB circuit is shown below:

iiBBrr

iiEE

iiCCiiBB

BB CC

EE

rr = ( = ( + 1) * + 1) * VVTT

IIEE@ @ = 1 and T = 25 = 1 and T = 25CC

rr = ( = ( + 1) * 0.026 + 1) * 0.026 IIEE

Recall:Recall: = I= IC C / I/ IBB

The Early Effect (Early Voltage)The Early Effect (Early Voltage)

VVCECE

IICCNote: Common-Emitter Note: Common-Emitter ConfigurationConfiguration

-V-VAA

IIBB

GreenGreen = Ideal I = Ideal ICC

OrangeOrange = Actual I = Actual ICC (I (ICC’)’)

IICC’ = I’ = ICC V VCECE + 1 + 1

VVAA

Early Effect ExampleEarly Effect Example

Given:Given: The common-emitter circuit below with IThe common-emitter circuit below with IBB = 25 = 25A, A, VVCCCC = 15V, = 15V, = 100 and V = 100 and VAA = 80. = 80.

Find: a) The ideal collector currentFind: a) The ideal collector current

b) The actual collector currentb) The actual collector currentCircuit DiagramCircuit Diagram

++__VVCCCC

IICCVVCECE

IIBB

= 100 = I= 100 = ICC/I/IBB

a)a)

IICC = 100 * I = 100 * IBB = 100 * (25x10 = 100 * (25x10-6-6 A) A)

IICC = 2.5 mA = 2.5 mA

b) Ib) ICC’ = I’ = ICC V VCECE + 1 + 1 = 2.5x10 = 2.5x10-3-3 15 + 1 15 + 1 = 2.96 mA= 2.96 mA

VVAA 80 80

IICC’ = 2.96 mA’ = 2.96 mA

Breakdown VoltageBreakdown VoltageThe maximum voltage that the BJT can withstand.The maximum voltage that the BJT can withstand.

BVBVCEOCEO = =The breakdown voltage for a common-emitter The breakdown voltage for a common-emitter biased circuit. This breakdown voltage usually biased circuit. This breakdown voltage usually ranges from ~20-1000 Volts.ranges from ~20-1000 Volts.

BVBVCBOCBO = = The breakdown voltage for a common-base biased The breakdown voltage for a common-base biased circuit. This breakdown voltage is usually much circuit. This breakdown voltage is usually much higher than BVhigher than BVCEOCEO and has a minimum value of ~60 and has a minimum value of ~60 Volts.Volts.

Breakdown Voltage is Determined By: Breakdown Voltage is Determined By:

• The Base WidthThe Base Width

• Material Being UsedMaterial Being Used

• Doping LevelsDoping Levels

• Biasing VoltageBiasing Voltage

SourcesSources

Dailey, Denton. Dailey, Denton. Electronic Devices and Circuits, Discrete and Integrated.Electronic Devices and Circuits, Discrete and Integrated.

Prentice Hall, New Prentice Hall, New Jersey: 2001. (pp 84-153)Jersey: 2001. (pp 84-153)11 Figure 3.7, Transconductance curve for a typical npn transistor, pg 90. Figure 3.7, Transconductance curve for a typical npn transistor, pg 90.

Liou, J.J. and Yuan, J.S. Liou, J.J. and Yuan, J.S. Semiconductor Device Physics and SimulationSemiconductor Device Physics and Simulation. . Plenum Press, New York: 1998.Plenum Press, New York: 1998.

Neamen, Donald. Neamen, Donald. Semiconductor Physics & Devices. Basic Principles.Semiconductor Physics & Devices. Basic Principles.

McGraw-Hill, Boston: 1997. (pp 351-409)McGraw-Hill, Boston: 1997. (pp 351-409)

Web SitesWeb Sites

http://www.infoplease.com/ce6/sci/A0861609.html