模拟电路模电课件及练习题答案ch01

SemiconductorMaterialsandProperties

ThePNJunction

DiodeCircuitsDC ysisandModels

DiodeCircuitsACEquivalentCircuit

OtherDiodeTypes

Ch1.SemiconductorMaterialsandDiodes

SemiconductorMaterialsandProperties

IntrinsicSemiconductor

本

Materialsconductivity

Conductor:conductionelectrons electricalconductivity

Insulator :electronsinbondingmechanism cannotmove

Semiconductor :silicon,germanium,galliumarsenide

砷化

Silicon,germanium single-crystalstructure

AttemperatureT=0oK,siliconisaninsulator.

WhenT reases, electronsand“holes”arecreated

浓度

Inpuresemiconductor,theconcentrationofelectrons

andholesareequal,andverysmall,soithasverysmallconductivity.

electron---

producedbythermalionization.

Hole---

emptypositioninbrokencovalentbond.

A electronisnegativechargeandaholeispositivecharge.

Doestheholecanmovethroughthecrystal ly?

Extrins杂i质cSemiconductor

phosphorus+silicon=N-typesemiconductor

Holespresentbecauseofthermalenergy

Whatarethemajoritycarriersinn-typematerials?

Redundantelectron

majoritycarriers

多数载流子：多子

杂质

DonorImpurity

Positivecharge

N-type semiconductor

minoritycarriers

少数载流子：少子

boron+silicon=P-typesemiconductor

WhatarethemajoritycarriersinP-typematerials?

AcceptNegati

rImpurityvecharge

Motionofholes

P-type

semiconductor

Hole

Conclusiononthedopedsemiconductor

Majoritycarrierisonlydeterminedbytheimpurity,buttoftemperature.

Minoritycarrierisstronglyaffectedbytemperature.

Ch1.SemiconductorMaterialsandDiodes

SemiconductorMaterialsandProperties

ThePNJunction

DiodeCircuits_DC ysisandModels

DiodeCircuits_ACEquivalentCircuit

OtherDiodeTypes

1.2.1 TheEquilibriumPNJunction

平衡

漂移 扩散

Driftanddiffusionofthecarriers

Drift：

themovementcausedbyelectricfields

Diffusion：

theflowcausedbyvariationsintheconcentration

1.2.1 TheEquilibriumPNJunctionHolesdiffusefromP-toN-region.ElectronsdiffusefromN-toP-region

P N

Demo

TheEquilibriumPNJunction

Depletionregion(space-chargeregion)_PNjunction

耗尽区

Electricfield Barrierregion 势垒区

P

space-chargeregion

N

E

Forward-BiasedPNJunction

正向偏置

PositivevoltageisappliedtoP,forward-biasedPN.

Thetwofieldsareopposite. Theresultsare:

Depletionregionisreduced,low .

MajoritycarriersflowacrossPNjunctionmoreeasily.

1.0

0.5

-1.0 -0.5 0.5 1.0 vD/V

反向偏置

PositivevoltageisappliedtoN,reverse-biasedPN.

Thetwofieldsareinthesamedirection.Theresultsare:

Depletionregionis reased,high .

Majoritycarrierscannotcrossthejunction.MinoritycarrierssweepacrossPNeasily.

iD/mA1.0

-1.0

iD=-IS

-0.5

0.5

0.5 1.0 vD/V

Thereversecurrentflowwillbeknownasthereversesaturation(orleakage)currentIS.

Whenthevoltageis r漏ea电s流edtosomepoint,

br击ea穿kdownoccursandcurrent reasesrapidly.The

voltageatthispointiscalledthebreakdownvoltage.

Avalanchebreakdown iD

Zenerbreakdown

iD=-IS

iD/mA1.0

0.5

VB

O vD

-1.0 -0.5 0.5 1.0 vD/V

1.2.4IdealCurrent-VoltageRelationship

Thecurrentisanexponentialfunctionofvoltage.

D S

i I(evD/VT 1)

IS reverse-biassaturationcurrent 反向饱和电流

VT thermalvoltageatroomtemperature

VT=0.026V

V turn-on,cut-in

温度电压

-1.0

iD=-IS

iD/mA1.0

0.5

0.5 1.0 v/V

voltage

导通电压，门槛电压

-0.5 D

i-vcharacteristic

Diode hasonePNjunctioninit

iD

vD

circuitsymbol

Photoofrealdiode

TemperatureEffect

T reases→requiredforward-biasvoltagedecrease

iDIS(evD/VT 1)

ISandVTarefunctionsofT.

JunctioncapacitanceCj

1

V 2

CjCj01 R

Vbi

VR appliedvoltage VR

P N

Vbi build-involtage

SwitchingTransient

Whenforward-bias,excesscarrierisstoredinbothregions.

Whenswitchingfromforwardtoreverse,itneedtimetoremove.

Storagetimets VD

Turn-offtimetf

P N

Lec01 华中

Ch1.SemiconductorMaterialsandDiodes

SemiconductorMaterialsandProperties

ThePNJunction

DiodeCircuits_DC ysisandModels

DiodeCircuits_ACEquivalentCircuit

OtherDiodeTypes

DiodeCircuits_DC ysisandModels

Models

Describingi-vcharacteristic,when yzingcircuit

Idealmodel

iD

iD

+vD-

Conductingstate

iD=0

iD

Reversebias

+vD-

+vD-

O vD

(a)

(vD<0,iD=0)

(b)

(vD<0,iD=0)

(c)

Piecewisemodel

Twolinearapproximations

Case1 Case2

Smallsignalmodel ACmodel

Whenadiodeisoperatinginthesmallrange，itcanbeasmall-signal remental .

Thatis:rd

vD

iD

iD

+

vD

rd

iD iD

∵iD

IS

(evD/VT 1) Q

small-signalconductance vD

IDQ

O vD

gd

diD

ISe

vD/VT Q

(a)

RoomT T=300K

(b)

Q

dvD

r

VT VT （ ）

r

V

T

d

I

26(mV)

DQ

I

DQ

(mA)

g

VT

∴d

d

IDQ

PS

PS

(a)Diodecircuit

(b)Conventional

circuit

E.g.1.1Determ hediodevoltageandcurrentforthecircuitshowninfigure,Assume

VPS=5V,R=2k

usingthegraphical ysis.Sol:Fordiode

iD/mA

Q-point

Loadline

vD/V

S

D

i I(evD/VT 1) 3.0

2.5

2.0

ForRandVPSbranch 2.2

VPSVDIDR 1.5

1.0

Findtwospecialpoints

(5V,0mA)and(0V,2.5mA)

0.5

00.621 2 3 4 5

Intersection quiescentpointorQ-point

静态工作点，直流工作点

PS

PS

(a)Diodecircuit

(b)Conventional

circuit

usingthemodel ysis.

IdealModel

VD0V IDVPS/R2.5mA

Piecewisemodel 1

Vγ 0.7V（SiliconDiode）

ID(VPSVγ)/R2.15mA iD

VPS

VPS

iD iD

Piecewisemodel 2 +

Vγ0.7V（SiliconDiode） D Vr D

Vr rf

Assume rf 0.2kΩ

I VPSVγ 1.95mA V=V+I r=1.09V

f

D Rr D D f

Ch1.SemiconductorMaterialsandDiodes

SemiconductorMaterialsandProperties

ThePNJunction

DiodeCircuits_DC ysisandModels

DiodeCircuits_ACEquivalentCircuit

OtherDiodeTypes

DiodeCircuits_ACEquivalentCircuit

Sinusoidal ysis

vIVPSvi

+

iD

vD _

IDQid vDVDQvd vOVOvo

iD Slope=gd=1/rd

+

vi_

+

V_PS

iDIDQ

vD

VDQ

+ +

iD

vl R vO

_ _

id

t

vd

t

IDQ

Q-point

O vD

VDQ

Sol:because vO

VO

vo

+ vD _

v

+

iD

i_

FortheDC ysis,wesetvi=0,then + +

IDQ

VPSVγ

50.6

0.88mA + vl

R vO

R 5

VOIDQR0.8854.4V

id

rd

v

o

FortheAC ysis,wesetVPS=0,then

V_PS _ _

Fig.1.34

d

rVT

IDQ

26mV0.88mA

0.0295kΩ

d

i vi

0.1sint

19.9sint(A)

rdR

0.02955

voidR0.0995sint(V)

Sol:

vO=VO+vo=4.4+0.0995sint（V）

+

vi_

+

+

+

vl

vD

iD

_

R

+

vO

vO/V

V_PS

_

_

4.4

O 2 3 4 t

Ch1.SemiconductorMaterialsandDiodes

SemiconductorMaterialsandProperties

ThePNJunction

DiodeCircuits_DC ysisandModels

DiodeCircuits_ACEquivalentCircuit

OtherDiodeTypes

OtherDiodeTypes

SolarCell 能电池

Itgetspowerfromthesolararrayandcanbeusedeithertopoweranelectricmotorortochargeabatterypack.

Photodiode 光电二极管

Itconvertsopticalsignalsintoelectricalsignals.

Light-EmittingDiode(LED)

Itconvertscurrentintolight.

发光二极管

SchottkyBarrierDiode 二极管

ThereisnominoritycarrierstorageintheSchottkydiode,sotheswitchingtimefromaforwardbiastoareversebiasisveryshortcomparedtothepnjunctiondiode.

ZenerDiode 二极管

1.SymbolandI-Vcharacteristic

k

Slope

a

(a)symbol (b)I-Vcharacteristic

2.Parameters

VZ Zenerbreakdownvoltage

rZ remental rZ=VZ/IZ

IZ Reverse-biascurrentwhenthediodeis

operatinginthebreakdownregion.

-VZ

-VZ0

iD/mA

O

-IZ(min)

vD/V

Slope 1 QrZ

IZ

VZ

-IZT

-IZ(max)

3.ZenerDiodeCircuits

E.g.1.3

Sol:

AssumeZenerdiodeVZ=5.6V,rZ=0andIZmax=3mA,findthevalueof .

VPSVZ

I

RVPSVZ

I

Question:

R

105.6

3

1.47kΩ

CanweeliminatetheR?Why?

IfVPSisrecedbysinusoidalinputvoltage

vi=15sinwt(V),plotoutputvoltagevOversusvi.

Zenerdiodeisusefulinavoltageregulator,oraconstant-voltagereferencecircuit.

RilimitsIzanddropsthe“excess”voltag weenVPSandVZ

WhenILisamax,andVPSisamin,IZisamin.WhenILisamin,andVPSisamax,IZisamax.Dueto

RVPSVZ

Weobtain

i IZ

IL

R(min) VPS(min)VZ (1)

i

and

IZ(min)IL

(max)

R(max) VPS(max)VZ (2)

i

I

(max)I(mi