me 6405 student lecture transistor

ME 6405 Student Lecture

Transistor

Sung-bum Kang

Keun Jae Kim Hongchul Sohn

Wenwei Xu

October 1, 2009

Georgia Institute of Technology

Contents

Introduction to Transistor(Speaker: Sung-bum Kang)

Field Effect Transistor(Speaker: Hongchul Sohn)

Power Transistor(Speaker: Wenwei Xu)

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44

Applications of Transistor(Speaker: Wenwei Xu)55

Bipolar Junction Transistor(Speaker: Keun Jae Kim)22

“Transistor” Part 1

Introduction to Transistor(Speaker: Sung-bum Kang)11



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44



Introduction

Question #1: How can we transfer original signal in long distance without loss?

Amplifier and Electronic Switch are needed.

Amplifier: any device that changes, usually increases, the amplitude of a signal. Electronic Switch: switch that the physical opening and closing is achieved by

applying appropriate electrical control signals.

Question #2: How can we control the TV with remote-controller?

Question #3: How can a computer recognize 0(off) and 1(on) for computing?

Introduction

Early 20th century, vacuum tube was used for the amplifier and switch.

ENIAC, the first general-purpose electronic

computer, contains 17,468 vacuum tubes.Vacuum Tube Radio

However, Vacuum Tube is too big, fragile, and energy-consuming.

Transistor solved this problem.

Introduction – Invention of Transistor

Invention In 1947, John Bardeen, Walter Brattain,

and William Schockly, researchers at Bell Lab, invented Transistor.

They found Transistor Effect: “when electrical contacts were applied to a crystal of germanium, the output power was larger than the input.”

In 1956, they were awarded the Nobel Prize in physics.

Transistor is a semiconductor device commonly

used to amplify or switch electronic signals.

John Bardeen, Walter Brattain,

and William Schockly

First model of Transistor, 1947

Introduction – Progress of Transistor

more than 2.9 billion transistors is packed into an area of fingernail

1941, Vacuum Tube

1948, the first (Germanium) TR

1954, Silicon TR

1958, Integrated Circuit

Sep 2009, 22nm silicon wafer

Now?

Edison effect

John Bardeen, Walter Brattain, and William Schockly

At TI Lab, Ease of processing, lower cost, greater power handling, more stable temperature characteristics

Intel CEO Paul Otellini, Sep 23 2009

Individual electronic components were soldered on to printed circuit boards.

IC placed all components in one chip.

Introduction – Underlying Science

Semiconductor is a basic building material of most integrated circuits. is a material that has an electrical resistivity between that of a

conductor and an insulator. has a few charge carriers(holes or free electrons) and may hence

be classified as almost insulator. However, the conductivity increases by adding impurities(doping).

Silicon is used in most commercial

semiconductors


Doping P(positive)-type doping is adding a certain type of atoms to the

semiconductor in order to increase holes. P-type semiconductor, acceptor

N(negative)-type doping is adding some amount of an element with more electrons in order to increase free electrons.

N-type semiconductor, donor

Add Group III(Boron)Add Group V (Phosphorous)


PN Junction is a junction formed by P-type and

N-type semiconductors together in very close contact.

Electrons(+) from n(-) region diffuse to occupy holes(-) in p(+) region.

Thin depletion region forms near junction.

What happens at the junction?


Forward bias -V pumps electrons into the N-region. +V pumps more holes into the P-region. Excess of charge in P and N region will

apply pressure on the depletion region and will make it shrink.

→ current flows

Backward bias -V sucked out electrons from N-region. +V sucked out holes from P-region. The depletion layer widens and it

occupies the entire diode(p-n). → current doesn’t flow

External Energy

Introduction – Types of Transistor

Transistor are categorized by Semiconductor material: germanium, silicon, gallium arsenide, etc.

Structure: BJT, FET, IGFET (MOSFET), IGBT

Polarity: NPN, PNP (BJTs); N-channel, P-channel (FETs)

Maximum power rating: low, medium, high

Maximum operating frequency: low, medium, high

Application: switch, audio, high voltage, etc.

Physical packaging: through hole, surface mount, ball grid array, etc.

Amplification factor Various Types of Transistor:

http://en.wikipedia.org/wiki/Category:Transistor_types

General Purpose Transistors Bipolar Junction Transistor (BJT) Field Effect Transistors (FET) Power Transistors




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44


Bipolar Junction Transistor(Speaker: Keun Jae Kim)

Introduction to Transistor(Speaker: Sung-bum Kang)11

22

BJT Introduction

PNP

NPN 3 Terminals

Base (B) Collector (C) Emitter (E)

2 Types: NPN, PNP Currents flow in opposite

direction NPN:

BE forward biased BC reverse biased

PNP: BE reverse biased BC forward biased

Georgia Institute of Technology 15

BJT Characteristics

IC is controlled by IB (Current Control) β (beta) is amplification factor for

transistor Typical value of is β 20 ~ 200

iE = iC + iB iC = βiB

VBE = VB – VE

VCE = VC - VE

Operating Regions

BJT Operating Regions

Operating Regions

Operating Region

Parameters Mode

Cut OffVBE < Vcut-in VCE > Vsupply

IB = IC = 0Switch OFF

LinearVBE = Vcut-in

Vsat < VCE < Vsupply

IC = β*IB

Amplification

Saturated

VBE = Vcut-in,VCE < Vsat

IB > IC,max, IC,max > 0

Switch ON


Georgia Institute of Technology 18

1) Cutoff Region: VBE < Vcut-in, iB = 0 iC = 0, VCE > Vsupply

2) Active / Linear Region: VBE = Vcut-in, iB > 0 iC = βiB, Vsat < VCE < Vsupply

3) Saturation Region: VBE = Vcut-in, iB > iC,max iC,max, VCE < Vsat

Vin

Vsupply


VSupplyVin

RB

RC

Question: What is the minimum Vin that can use the transistor as an amplifier?

Given:• RB = 10 kΩ• RC = 1 kΩ • β = 100• VSupply = 10 V• Vcut-in = 0.7 V• Vsat = 0.2 V

iB = iC / β = 0.0098/100 = 0.098mA

BJT as Amplifier

Vin - iB*RB – VBE = 0

Vsupply – iC *RC – VCE=0

iC = (Vsupply – VCE) / RC

Set VCE = Vsat = 0.2V

iC = (10 – 0.2) / 1000 = 9.8mA

iC = βiB

Vin = iB*RB + VBE

Set VBE = Vcut-in = 0.7V

Vin = 0.098*(10-3)*10000 + 0.7V

Vin = 1.68V or greater.

From

3rd Exercise

Turns on/off coils digitally

BJT as Switch

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55

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11 Introduction to Transistor(Speaker: Sung-bum Kang)



Applications of Transistor(Speaker: Wenwei Xu)

Bipolar Junction Transistor(Speaker: Keun Jae Kim)


Field-Effect Transistors

Basics Conduction of a “channel” is controlled by electric field effect

Three terminals: gate, source, drain

Voltage-controlled current device

control terminal

current channel

of charge carriers for charge carriers

control voltage

Very little current flows through input (gate) terminals


BJT vs. FET What was BJT then?

A current-controlled current device

Comparison


Types JFET (Junction FET)

MOSFET (Metal-oxide-semiconductor FET)

MESFET (Metal-semiconductor FET)

HFET (Hetero-structure FET)

MODFET (Modulation doped FET)

IGBT (Insulated-gate bipolar transistor)

Power MOSFETs

FREDFET (Fast reverse or fast recovery epitaxial diode FET)

ISFET (Ion-sensitive FET)

DNAFET

JFET (Junction FET)

MOSFET (Metal-oxide-semiconductor FET)

JFETs

JFETs n-channel

General Properties Advantages: Much higher input resistance, lower noise, easier

fabrication, ability to handle higher currents and powers

Disadvantages: Slower speeds in switching circuits, smaller bandwidth for a given gain in an amplifier

p-channel

n-channel JFET

Characteristics

n-channel JFET

Characteristics Idealized Static

2(1 )GSD DSS

P

vi I

V

n-channel JFET

Characteristics Practical Static

2(1 ) (1 )GS DSD DSS

P A

v vi I

V V

Transfer

MOSFETs

MOSFETs or Insulated-gate FET (IGFET)

n-channel Enhancement

General Properties Input resistance even higher

Used primarily in digital electronic circuits

Provide controlled-source characteristics in amplifier circuits

n-channel Depletion

n-channel Enhancement MOSFET

Characteristics

n-channel Enhancement MOSFET

Characteristics Practical

2( ) (1 )DSD GS T

A

vi K v V

V 2[2( ) ]D GS T DS DSi K v V v v

n-channel Depletion MOSFET

Characteristics Practical

2[2(1 )( ) ( ) ]GS DS DSD DSS

P P P

v v vi I

V V V 2(1 ) (1 )GS DS

D DSSP A

v vi I

V V

Task: Design a n-channel common-source JFET Amplifier

Amplifiers, Switches

Applications

You CAN do it!! Psst! You can read it!!http://www.electronics-tutorials.ws/amplifier/amp_3.html


Introduction to Transistor(Speaker: Sung-bum Kang)



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Applications of Transistor(Speaker: Wenwei Xu)


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55

Power Transistor

Concerned with delivering high power Used in high voltage and high current application

In generalFabrication process different in order to: Dissipate more heat Avoid breakdownLower gain than signal level transistor

Power BJT

Same structure to the signal level BJT The active area is distinctively higher-high current

capacity Thick and low-doped collector region Large heat dissipation--- larger dimensions

Power MOSFET

Same working principles to MOSFET

Designed to handle large power

Low internal voltage drop and high current capacity

High commutation speed and good efficiency at low voltages—high speed switch

Applications of Transistorbuilding blocks for modern electronics

Digital logic circuits Microprocessors, microcontrollers, chips (TTL) Photo-transistors Replaces normal switches, mechanical relays. A/D converter Encoders Multiplexers Power supplies

more…

microprocessorwireless

communicationmotor

headphone, microphone

Applications(cont.)

– Switch for a digital signal: BJT or MOSFET – Switch for a analog signal: JFET – Switch for a power signal: Power MOSFET or BJT – Current controlled-current amplifier: BJT – Voltage controlled-current amplifier: JFET or MOSFET

Small input voltage and large output currentoperated in the cut-off region(open) and saturation region(close)

Example: 2N3904 NPNAssuming LED requires 20-40 mA to provide a bright display and has 2 voltage drop when forwarded biased

Output=0V—offOutput=5V---on, the transistor is in saturation, with base current

(5 0.7 ) /10 0.43BI V V K mA

Collector current (LED current) is limited by collector resistor

mAVVVIC 28100/)2.025(

BJT as switches

BJT as amplifiers

Audio amplifiers, radio frequency amplifiers, regulated power supplies

Low input impedance and high voltage gain

ExampleSpeaker amplifier

BJT series produce higher gain

Applications of FET

Advantages of FET over BJT They are devices controlled by voltage with a very high input

impedance (107 to 1012 ohms) FETs generate a lower noise level than the Bipolar Junction

Transistor (BJT) FETs are more stable than BJT with temperature FETs are easier to manufacture than the BJT, because they require

fewer steps to be built and they allow more integrated devices in the same IC

FETs behave like resistors controlled by voltage for small drain-source voltage values

The high input impedance of FET allows them to withhold loads long enough to allow its usage as storage elements

Power FETs can dissipate higher power and can switch very large currents.

Applications of FET

Amplifiers•Small Signal•Low Distortion•High Gain•Low Noise amplifier•Selectivity•High-Frequency

Switches•Chopper-Type•Analog Gate•Communicator

Protection Diodes•Low-leakage

Current LimitersResistorsMixersOscillators

FET as analog switch-example

When VGS = 0, FET becomes saturated and it behaves like a small resistance(<100 ohm) and, therefore,

VOUT = {RDS/ (RD + RDS (ON))}* Vin

RD>>RDS, VOUT → 0

When a negative voltage equal to VGS (OFF) is applied to the gate, the FET operates in the cut-off region and it acts like a very high resistance usually of some mega ohms. Hence output voltage becomes nearly equal to input voltage.

Contact information(in order of presenting)

Sung-bum Kang [email protected] Keun Jae Kim [email protected] Hongchul Sohn [email protected] Wenwei Xu [email protected]

References www.wikipedia.org www.google.com

“Introduction to Electrical Engineering”, Mulukata S. Sarma, Oxford University Press, 2001, Chap. 7.4~8.4. Fall 2008 Transistors Slides http://www-g.eng.cam.ac.uk/mmg/teaching/linearcircuits/index.html http://en.wikipedia.org/wiki/FET http://en.wikipedia.org/wiki/JFET http://en.wikipedia.org/wiki/MOSFET http://www.slideshare.net/guest3b5d8a/fets “Introduction to Electrical Engineering”, Mulukata S. Sarma, Oxford University Press, 2001, Chap. 7.4~8.4. Fall 2008 Transistors Slides http://www-g.eng.cam.ac.uk/mmg/teaching/linearcircuits/index.html http://en.wikipedia.org/wiki/FET http://en.wikipedia.org/wiki/JFET http://en.wikipedia.org/wiki/MOSFET http://www.slideshare.net/guest3b5d8a/fets

http://www.electronics.dit.ie/staff/ypanarin/Lecture%20Notes/K235-1/2%20Transistor-Thyristor.pdf http://ecee.colorado.edu/~bart/book/book/chapter5/ch5_9.htm http://www.ece.mtu.edu/labs/EElabs/EE3305/Bipolar_Junction_Transistors.pdf http://www.partminer.com/glossaryhtml/bjt.htm http://www.lycos.com/info/bipolar-junction-transistor--applications.html http://jimwarholic.com/uploaded_images/power-supply-768753.jpg http://abbydamico.files.wordpress.com/2008/09/microprocessor-athlon-64.jpg http://www.billfrymire.com/blog/wp-content/uploads/2008/05/wireless-communication-connection-1000.jpg http://www.cybermediatech.com/images/WirelessHeadphone-big.jpg http://www.colorado.edu/physics/phys3330/phys3330_fa09/pdfdocs/AN101FETintro.pdf http://www.circuitstoday.com/fet-applications

Thank you!

me 6405 student lecture transistor

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