Me 6405 student lecture
Download
1 / 40

ME 6405 Student Lecture - PowerPoint PPT Presentation


  • 125 Views
  • Uploaded on

ME 6405 Student Lecture. Transistors. Angela Sodemann Jin Yang Louis Nucci . Saturday, May 31, 2014. Lecture outline. Brief History of Transistors Introduction to Transistors Bipolar Junction Transistors (BJT) Field Effect Transistors (FET) Power Transistors. Transistor History.

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about 'ME 6405 Student Lecture' - niran


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
Me 6405 student lecture
ME 6405 Student Lecture

Transistors

Angela Sodemann Jin Yang Louis Nucci

Saturday, May 31, 2014

Georgia Institute of Technology


Lecture outline
Lecture outline

  • Brief History of Transistors

  • Introduction to Transistors

  • Bipolar Junction Transistors (BJT)

  • Field Effect Transistors (FET)

  • Power Transistors

Georgia Institute of Technology


Transistor history
Transistor History

Invention of transistors is a milestone of modern microelectronics industry

  • Invention:

    • 1947, at Bell Laboratories, by John Bardeen, Walter Brattain, and William Schockly (a three-point transistor, made with Germanium)

    • 1956, They received Nobel Prize in Physics "for their researches on semiconductors and their discovery of the transistor effect"

    • First application: replacing vacuum tubes (big & inefficient)

  • Today:

    • Advanced microprocessor uses as many as 1.7 billion transistors (MOSFETs)

First model of Transistor

Georgia Institute of Technology


Packaging format of transistor
Packaging Format of Transistor

  • Two main categories:

    • Through-Hole

    • Surface-Mount

  • Packaging Materials:

    • Glass, metal, ceramics or plastic

Through-hole transistor

Surface Mount Transistor

  • Large transistor array uses latest Ball grid array (BGA) packaging

  • Power transistors have large packages clamped to heat sinks for enhanced cooling

Georgia Institute of Technology


What is transistor
What is Transistor ?

  • Definition:

    Transistor is three-terminal, solid-state semiconductor device

  • Function:

    Control electric current or voltage between two of the terminals by applying an electric current or voltage to third terminal. Transistor is an active component.

  • Application:

    • Switch in digital circuits

      Two operating positions: on and off. This switching capability allows binary functionality and permits to process information in a microprocessor

    • Amplifier in analog circuits

Georgia Institute of Technology


Transistor chemistry
Transistor Chemistry

  • Silicon

    • Semiconductor that is able to be doped with other elements to adjust its electrical response

  • Arsenic, phosphorous

    • N-type dopants which add an electron to the silicon

  • Boron, aluminum

    • P-type dopants which have an extra “hole”

Georgia Institute of Technology


Pn junction
PN Junction

  • It is also called Junction Diode

  • Allows current to flow from P to N only

  • Electronsfrom n regiondiffuse to occupy holes in pregion

  • Thin depletion region forms near junction, resulting in contact potential (For silicon, on order of 0.6-0.7 V)

  • Two types of behavior: Forward and Reverse biased

Georgia Institute of Technology


Pn junction forward biased
PN Junction – Forward Biased

http://www.tpub.com/neets/book7/25k.htm

Georgia Institute of Technology


Pn junction reverse biased
PN Junction – Reverse Biased

http://www.tpub.com/neets/book7/25k.htm

Georgia Institute of Technology


Types of transistor
Types of Transistor

Two Main Categories:

  • Bipolar Junction Transistor - BJT

  • Field Effect Transistor - FET

    • JFET - Junction FET

    • MOSFET - Metal Oxide Semiconductor FET

Georgia Institute of Technology


BJT

Georgia Institute of Technology


Bipolar junction transistor

npn bipolar junction transistor

Bipolar Junction Transistor

  • 3 adjacent doped regions (each layer connected to a lead)

    • Base (B)

    • Collector (C)

    • Emitter (E)

  • 2 types of BJT:

    • npn

    • pnp

  • Most common type: npn

pnp bipolar junction transistor

Georgia Institute of Technology


Npn bjt
npn BJT

  • 1 thin layer of p-type silicon, sandwiched between 2 layers of n-type silicon

  • Emitter is more heavily doped than collector

  • With VC>VB>VE:

    • Base-Emitter junction forward biased, Base-Collector reverse biased.

    • Electrons diffuse from Emitter to Base (from n to p)

    • Depletion layer on the Base-Collector junction no flow of electron allowed

    • BUT Base is thin and Emitter region is heavily doped  electrons have enough momentum to cross Base into Collector

    • Small base current IB controls large current IC, functioning as a current amplifier

Georgia Institute of Technology


Bjt characteristics

β (beta) is amplification factor for transistor (often called hFE by manufacturers)

β is temperature and voltage dependent, no precise relationship can be assumed when designing transistor circuit

β varies a lot among transistors (for typical BJT: on order of 100)

IC is controlled by IB (Current Control)

BJT Characteristics

Georgia Institute of Technology


Common emitter transistor circuit
Common Emitter Transistor Circuit called

  • Emitter is grounded and input voltage is applied to Base

  • Base-Emitter starts to conduct when VBE is about0.6V, IC flows with IC= β*IB

  • As IB further increases, VBE slowly increases to 0.7V, IC rises exponentially

  • As IC rises, voltage drop across RC increases and VCE drops toward ground (transistor in saturation, no more linear relation between IC and IB)

Georgia Institute of Technology


Common emitter characteristics
Common Emitter Characteristics called

Collector current IC proportional to Base current IB

Collector current controlled by the collector circuit (Switch behavior)

In full saturation VCE=0.2V

No current flows

Georgia Institute of Technology


Operation point of bjt in active region

Biased Point Q called

Load-line curve

Operation Point of BJT in Active Region

  • Every IB has corresponding I-V curve.

  • Applying Kirchoff laws to base, emitter and collector circuits

Georgia Institute of Technology


Operation region summary
Operation Region Summary called

Georgia Institute of Technology


Bjt as switch
BJT as Switch called

When Vin < 0.7V

  • BE junction not forward biased

  • Cutoff state of transistor

  • IC=IE=0

  • Vout = VCE=VC

    Vout= High

When Vin > 0.7

  • BE junction forward biased

    (VBE=0.7V)

  • IB = (Vin-VB)/RB

  • Saturation region

  • VCE small (~0.2 V for saturated BJT)

    Vout= Low

Georgia Institute of Technology


Practical example led switch
Practical Example – LED Switch called

Transistor model is known: 2N3904 npn

Assuming LED requires 20-40 mA to provide a bright display and has 2 voltage drop when forwarded biased;

  • When digital output is 0V, transistor is off

  • When digital output is 5V, the transistor is

    in saturation, with base current

Collector current (LED current) is limited

by collector resistor

LED is lighted

Georgia Institute of Technology


Bjt as amplifier
BJT as Amplifier called

  • Assume Gain β= 100

  • Assume BJT in active region VBE=0.7V

Georgia Institute of Technology


Practical example speaker amplifier
Practical Example – Speaker Amplifier called

Georgia Institute of Technology


FET called

Georgia Institute of Technology


Field effect transistor
Field Effect Transistor called

  • Described as a transconductance amplifier, meaning output current is controlled by an input voltage

  • Contrarily, BJT is a current amplifier, a large output current is controlled by a much smaller base current

  • In structure, FET is similar to BJT:

    • Three terminals

  • Different terminal names

Georgia Institute of Technology


Types of field effect transistor
Types of Field Effect Transistor called

  • Types of Field Effect Transistors

    • MOSFET (metal-oxide-semiconductor field-effect transistors)

      • Enhancement mode

      • Depletion mode

    • JFET (Junction Field-effect transistors)

    • MESFET (Metal Semiconductor Field-effect transistor)

    • HFET (Heterostructure Field-effect transistor)

    • MODFET (Modulation Doped Field-effect transistor)

  • Mostly used one is n-channel enhancement mode MOSFET, also called NMOS

Conducting Region

Nonconducting Region

Nonconducting Region

Enhanced n-MOSFET

Depleted MOSFET

JFET

Georgia Institute of Technology


N channel enhancement mode mosfet

Enhancement mode called

n-channel Enhancement Mode MOSFET

  • N-channel => Source and Drain are n type

  • Enhancement mode =>

    Increase VGS to make the travel from D to S easier for the electrons

Georgia Institute of Technology


Modes of mosfet
Modes of MOSFET called

  • Enhancement mode

    • Sub-threshold – Vg < Vth

      • Transistor is off

    • Linear Region – Vg > Vth and Vds < Vgs-Vth

      • Transistor is on

    • Saturation – Vg > Vth and Vds > Vgs-Vth

      • Transistor is on, with a portion of the channel being off

  • Depletion mode

    • Similar to enhancement, always on, use negative voltage

  • Power mode

    • Better behavior in saturation

Georgia Institute of Technology


Nmos characteristics

For V called DS > VPinchoff , the base current is a function of VGS

Active region

Saturation region

Pinchoff Point

NMOS Characteristics

Georgia Institute of Technology


Nmos behavior

VGS <Vth called

IDS=0

NMOS Behavior

VGS > Vth :

0 < VDS < VPinch off

Depletion mode (or active region), gate holes are repelled.

 variable resistor (controled by VGS)

VDS > VPinch off

Inversion mode (or saturation region), IDS constant.

VDS > VBreakdown

IDS increases quickly

Should be avoided

Georgia Institute of Technology


Symbols of fet
Symbols of FET called

Georgia Institute of Technology


JFET called

Can be used with VG < 0

N-type

N- doping is

done by adding carrier electrons,

phosphorus, arsenic, and antimony

Georgia Institute of Technology


JFET called

Can be used with VG=0

P-Type

P- doping is

done by adding boron to

silicon to create holes

Georgia Institute of Technology


Jfet behavior
JFET Behavior called

Georgia Institute of Technology


Application of fet
Application of FET called

  • Switch

  • Voltage Controlled Resistor

  • Small Signal Amplifier

Georgia Institute of Technology


Differences between bjt and fet
Differences Between BJT and FET called

Georgia Institute of Technology


Power transistor
Power Transistor called

  • In General

    • Power transistor is one that has a power dissipation of 1W or more

    • Conduct a large maximum collector current and have maximum collector power dissipation

    • Interface from low-output current devices such as IC and computer ports to other devices requiring large currents

    • Generally shielded by or have a structure with heat sinks in order to dissipate more heat

  • BJT Power Transistor

  • FET Power Transistor

Georgia Institute of Technology


Application of bjt power transistor
Application of BJT Power Transistor called

Used in LCD Inverter

From Toshiba Semiconductor Company

http://www.semicon.toshiba.co.jp

Georgia Institute of Technology


Application of bjt power transistor1
Application of BJT Power Transistor called

Used in Battery Charger

From Toshiba Semiconductor Company

http://www.semicon.toshiba.co.jp

Georgia Institute of Technology


Application of mosfet power transistor
Application of MOSFET Power Transistor called

Used in Battery Protection Circuit

www.Lovoltech.com

Georgia Institute of Technology


References
References called

  • David G. Alciatore and Michael B. Histand, “Introduction to Mechatronics and Measurement Systems”, Second Edition, Mc Graw Hill, 2002

  • http://en.wikipedia.org

  • http://www.semicon.toshiba.co.jp

  • http://www.brookdale.cc.nj.us/fac/engtech/aandersen/engi242/powerpoint

  • Old student lecture slides

Georgia Institute of Technology


ad