IGBT's and MOSFET's

8/13/2019 IGBT's and MOSFET's

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IGBTS ND MOSFETS


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Source

Drain

Gate Valve

ArteryVein

Emitter Collector

Base


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N P

W

Vappl< 0

-+

P N

W

Vappl> 0

-+

Holes from P region (Emitter) of 1st

PN junctiondriven by FB of 1stPN junction into central N region (Base)

Driven by RB of 2ndPN junction from Base into P region of2ndjunction (Collector)


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The metal-oxide semiconductor field-effecttransistor MOSFET): the gate is insulatedfrom the channel by a silicon dioxide (SiO2)

layer


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Two types of MOSFETs depletion type (D-MOSFETs) have aphysical

channelbetween Drain and Source, with novoltage applied to the Gate

enhancement type (E-MOSFETs) have no physicalDrain-Source channel


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D-MOSFET Channel may be

enhanced orrestricted by gatevoltage

E-MOSFET

Channel is created bygate voltage


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If the MOSFET is an n-

channel or nMOSFET,

then the source and drain

are 'n+' regions and the

body is a 'p' region.

If the MOSFET is a p-

channel or pMOSFET,

then the source and drain

are 'p+' regions and the

body is a 'n' region.

Substrate

Channel Drain

Insulator

Gate

Source


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A cross section through an nMOSFET when the gate voltage

VGSis below the threshold for making a conductive channel;

there is little or no conduction between the terminals drain

and source; the switch is off.

When the gate is more positive, it attracts electrons, inducingan n-type conductive channel in the substrate below the

oxide, which allows electrons to flow between the n-doped

terminals; the switch is on


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Substrate

ChannelDrain

Insulator

Gate

VSG> 0n type operation

Positive gate bias attracts electrons into channelChannel now becomes more conductive

Moreelectrons

Source

VSD

VSG


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G

pn+n+

metal

S DB

oxide

+-

+++

+++

- - - -

VGS1>Vt

pn+n+

metal

S DB

oxide

+-

+++

++++++

- - - - - -

VGS2>VGS1

pn+n+

metal

S DB

oxide

+-

+++

++++++

- - - - - - - - -

VGS3>VGS2+++

ID

VDS

0.1 v

increasingVGS

Increasing VGSputs more chargein the channel, allowing moredrain current to flow

cut-off


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p

n+n+

metal

source

S

gate

Gdrain

D

body

B

oxide

+-

+++

++++++

VDS large

As the drain voltage increases, the differencein voltagebetween the drain and the gate becomes smaller. Atsome point, the difference is too small to maintain thechannel near the drain pinch-off


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0

0 0

0

VG VG

0 VD

VG VG

once pinch-off occurs, there is no

further increase in drain current


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Cut-off: VGSVT

and VDS

< VGS

-

VT

Saturation:

VGS>VTand VDS> VGS-VT


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IGBT(Insulated Gate Bipolar Transistor) is a voltage-controlled

power transistor,

similar to the power MOSFET in operation and construction.

These devices offer superior performance to the bipolar-

transistors.They are core cost- effective solution in high power, wide

range of frequency applications

THE SIMPLE ADDITION OF A EXTRA P-N JUNCTION TOTHE DRAIN OF THE MOSFET CHANGES THIS UNIPOLAR

DEVICE INTO BIPOLAR JUNCTION TRANSISTOR.

Whats an IGBT ?


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Construction & Operation of IGBT

GATE EMITTER

COLLECTOR

N NP P

N-

P+N+

Structure Of IGBT

COLLECTOR

GATE

EMITTER

Equivalent Circuit

The operation of the IGBT simply can be treated as a

partitioning of anN-channel MOSFET and a PNP bipolar transistor.

The IGBT functions as a bipolar transistor that is supplied

base current by a MOSFET.


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TURN-ON

The presence of the substrate creates a junction J1between the P+ and the N zone of the body.

When the positive gate bias allows the inversion of

the P base region under the gate, an N channel iscreated, with a flow of electrons, generating acurrent in the exact same way as a Power MOSFET.


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TURN-OFF When a negative bias is

applied to the gate or the

gate voltage falls belowthe threshold value, thechannel is inhibited andno holes are injected inthe N- region.

REVERSE BLOCKING When a negative voltage

is applied to the collectorthen J1 is reverse biasedand the depletion layerexpands to the N- region.


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FORWARD BLOCKING.When gate and emitter are shorted and a positive voltage

is applied to the collector terminal the P/N- theJ3 junctionis reverse biased. Again it is the depletion layer in the N-drift region that withstands the voltage applied


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IGBT

Module & Discrete

F.A.

- Inv erter,

AC s ervo,

Robot ics

Power Supp ly

- UPS, SMPS

Elevator

IndustrialApplications of IGBT

Transportat ion

-Ign it ion con trol,

Bat tery chargerWelding

machine


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IH-Cooker

IH-Jar

(Rice Cooker)

4|00

MWO

12:30

IGBTModule & Discrete

Inverter

Air -condi t ioner

Consumer Applications of IGBT

Washing

machine

Camera

Strobo


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HIGH VOLTAGE

HIGH CURRENT

HIGH FREQUENCY

GTO

BJT

IGBT

MOSFET

FREQUENCY

POWER

1 70 1000KHZ

IGBT Operation Area

25 KW

10

1

0.1


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THANK

YOU

QUES AND ANSSESSION

IGBT's and MOSFET's

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