Lic ic fabrication

iv sem anna university syllabus ppt

1. 1
UNIT-I
IC FABRICATION

2. 2
Anintegratedcircuit(IC)isaminiature,low
costelectroniccircuitconsistingofactiveand
passivecomponentsfabricatedtogetherona
singlecrystalofsilicon.Theactivecomponentsare
transistorsanddiodesandpassivecomponentsare
resistorsandcapacitors.
INTEGRATED CIRCUITS

3. 3
Advantages of integrated circuits
1.Miniaturization and hence increased
equipment density.
2.Cost reduction due to batch processing.
3.Increased system reliability due to the
elimination of soldered joints.
4.Improved functional performance.
5.Matched devices.
6.Increased operating speeds.
7.Reduction in power consumption

4. 4
Basic processes involved in fabricating
Monolithic ICs
1. Silicon wafer (substrate) preparation
2. Epitaxial growth
3. Oxidation
4. Photolithography
5.Diffusion
6.Ion implantation
7.Isolation technique
8.Metallization
9.Assembly processing & packaging

5. 5
Silicon wafer (substrate) preparation
1.Crystalgrowth&doping
2.Ingottrimming&grinding
3.Ingotslicing
4.Waferpolicing&etching
5.Wafercleaning
Typical wafer

6. 6

7. 7
Epitaxial growth
1.Epitaxy means growing a single crystal
silicon structure upon a original silicon
substrate, so that the resulting layer is an
extension of the substrate crystal structure.
2.The basic chemical reaction in the
epitaxial growth process of pure silicon is the
hydrogen reduction of silicon tetrachloride.
1200
o
C
SiCl+ 2H <-----------> Si + 4 HCl

8. 8

9. 9
Oxidation
1.SiO
2isanextremelyhardprotectivecoating&is
unaffectedbyalmostallreagentsexceptby
hydrochloricacid.Thusitstandsagainstany
contamination.
2.ByselectiveetchingofSiO
2,diffusionof
impuritiesthroughcarefullydefinedthrough
windowsintheSiO
2canbeaccomplishedto
fabricatevariouscomponents.

10. 10
Oxidation
Thesiliconwafersarestackedupinaquartzboat&
theninsertedintoquartzfurnacetube.TheSiwafers
areraisedtoahightemperatureintherangeof950
to1150
o
C&atthesametime,exposedtoagas
containingO
2orH
2Oorboth.Thechemicalactionis
Si+2HO----------->SiO
2+2H2

11. 11

12. 12

14. 14
Oxidation
oxide
thicknesst t
time, t

15. 15

16. 16

17. Photolithography
Theprocess ofphotolithography
makes itpossible toproduce
microscopicallysmallcircuitanddevice
patternonsiwafer
Two processes involved in photolithography
a) Making a photographic mask
b) Photo etching

18. 18

19. 19
Photographic mask
Thedevelopmentofphotographicmask
involvesthepreparationofinitialartworkand
itsdiffusion.reduction,decompositionofinitial
artworkorlayoutintoseveralmasklayers.
Photo etching
Photoetchingisusedfortheremovalof
SiO
2fromdesiredregionssothatthe
desired2impuritiescanbediffused

20. 20

21. 21
Diffusion
Theprocessofintroducingimpuritiesinto
selectedregionsofasiliconwaferiscalled
diffusion.Therateatwhichvariousimpurities
diffuseintothesiliconwillbeoftheorderof
1µm/hratthetemperaturerangeof900
0
Cto
1100
0
C.Theimpurityatomshavethetendency
tomovefromregionsofhigherconcentrations
tolowerconcentrations

22. 22

23. 23
Ion implantation technique
1.Itisperformedatlowtemperature.Therefore,
previouslydiffusedregionshavealesser
tendencyforlateralspreading.
2.Indiffusionprocess,temperaturehastobe
controlledoveralargeareainsidetheoven,
whereasinionimplantationprocess,
acceleratingpotential&beamcontentare
dielectricallycontrolledfromoutside.

24. 24

25. 25
Dielectric isolation
Indielectricisolation,alayerofsoliddielectric
suchasSiO
2orrubycompletelysurroundseach
componentstherebyproducingisolation,both
electrical&physical.Thisisolatingdielectriclayeris
thickenoughsothatitsassociatedcapacitanceis
negligible.Also,itispossibletofabricatebothpnp&
npntransistorswithinthesamesiliconsubstrate.

26. PN JUNCTION ISOLATION
26

27. 27

28. 28
Aluminium is preferred for metallization
1.Itisagoodconductor
2.itiseasytodepositaluminiumfilmsusingvacuum
deposition.
3.Itmakesgoodmechanicalbondswithsilicon
4.Itformsalowresistancecontact

29. 29

30. 30

31. 31
IC packages available
1.Metal can package.
2.Dual-in-line package.
3.Ceramic flat package.

32. DIODE
32

33. FABRICATION OF
TRANSISTOR
33

34. 34

35. 35

36. CAPACITOR FABRICATION
36

37. 37

38. FABRICATION OF RESISTOR
38

39. 39

40. CMOS COPLEMMENTRY
MOSFET
40

41. CROSS SECTIONAL VIEW OF CMOS
41

42. JFET
42

43. N-CHANNEL JFET
43

44. 44
UNIT-II
Characteristics of Op-Amp

45. 45
OPERATION AMPLIFIER
Anoperationalamplifierisadirectcoupledhighgain
amplifierconsistingofoneormoredifferentialamplifiers,
followedbyaleveltranslatorandanoutputstage.
Itisaversatiledevicethatcanbeusedtoamplifyac
aswellasdcinputsignals&designedforcomputing
mathematicalfunctionssuchasaddition,subtraction
,multiplication,integration&differentiation

46. 46
Op-amp symbol
Non-inverting input
inverting input
0utput
+5v
-5v
2
3
6
7
4

47. 47
Ideal characteristics of OPAMP
1.Openloopgaininfinite
2.Inputimpedanceinfinite
3.Outputimpedancelow
4.Bandwidthinfinite
5.Zerooffset,ie,Vo=0whenV1=V2=0

48. 48
Inverting Op-AmpV V
R
R
OUT IN
f

1

49. 49
Non-Inverting AmplifierV V
R
R
OUT IN
 





1
1
2

50. 50
Voltage follower

51. 51
DC characteristics
Input offset current
Thedifferencebetweenthebiascurrentsatthe
inputterminalsoftheop-ampiscalledasinputoffset
current.Theinputterminalsconductasmallvalueofdc
currenttobiastheinputtransistors.Sincetheinput
transistorscannotbemadeidentical,thereexistsa
differenceinbiascurrents

52. 52
DC characteristics
Input offset voltage
Asmallvoltageappliedtotheinputterminalsto
maketheoutputvoltageaszerowhenthetwoinput
terminalsaregroundediscalledinputoffsetvoltage

53. 53
DC characteristics
Input offset voltage
Asmallvoltageappliedtotheinputterminalsto
maketheoutputvoltageaszerowhenthetwoinput
terminalsaregroundediscalledinputoffsetvoltage

54. 54
DC characteristics
Input bias current
Input bias current IB as the average value of
the base currents entering into terminal of an op-amp
I
B=I
B
+
+ I
B
-
2

55. 55
DC characteristics
THERMAL DRIFT
Biascurrent,offsetcurrentandoffsetvoltage
changewithtemperature.Acircuitcarefullynulledat
25
o
cmaynotremainsowhenthetemperaturerisesto
35
o
c.Thisiscalleddrift.

56. 56
AC characteristics
Frequency Response
HIGH FREQUENCY MODEL OF OPAMP

57. 57
AC characteristics
Frequency Response
OPEN LOOP GAIN VS FREQUENCY

58. 58
Need for frequency compensation in
practical op-amps
•Frequencycompensationisneededwhenlarge
bandwidthandlowerclosedloopgainisdesired.
•Compensatingnetworksareusedtocontrolthephase
shiftandhencetoimprovethestability

59. 59
Frequency compensation methods
•Dominant-pole compensation
•Pole-zero compensation

60. 60
Slew Rate
•Theslewrateisdefinedasthemaximumrateofchange
ofoutputvoltagecausedbyastepinputvoltage.
•Anidealslewrateisinfinitewhichmeansthatop-amp’s
outputvoltageshouldchangeinstantaneouslyin
responsetoinputstepvoltage

61. 61
UNIT-III
Applications of Op Amp

62. 62
Instrumentation Amplifier

63. 63
Instrumentation Amplifier
Inanumberofindustrialandconsumer
applications,themeasurementofphysicalquantitiesis
usuallydonewiththehelpoftransducers.Theoutputof
transducerhastobeamplifiedSothatitcandrivethe
indicatorordisplaysystem.Thisfunctionisperformed
byaninstrumentationamplifier

64. 64
Features of instrumentation amplifier
1.highgainaccuracy
2.highCMRR
3.highgainstabilitywithlowtemperatureco-
efficient
4.lowdcoffset
5.lowoutputimpedance

65. 65
Differentiator

66. 66
Integrator

67. 67
Differential amplifier

68. 68
Differential amplifier
Thiscircuitamplifiesonlythedifference
betweenthetwoinputs.Inthiscircuitthere
aretworesistorslabeledR
INWhichmeans
thattheirvaluesareequal.Thedifferential
amplifieramplifiesthedifferenceoftwo
inputswhilethedifferentiatoramplifiesthe
slopeofaninput

69. 69
Summer

70. 70
Comparator
Acomparatorisacircuitwhichcompares
asignalvoltageappliedatoneinputofan
op-ampwithaknownreferencevoltageat
theotherinput.Itisanopenloopop-amp
withoutput+Vsat

71. 71
Comparator

72. 72
Applications of comparator
1.Zerocrossingdetector
2.Windowdetector
3.Timemarkergenerator
4.Phasedetector

73. 73
Schmitt trigger

74. 74
Schmitt trigger
Schmitttriggerisaregenerativecomparator.It
convertssinusoidalinputintoasquarewave
output.TheoutputofSchmitttriggerswings
betweenupperandlowerthresholdvoltages,
whicharethereferencevoltagesoftheinput
waveform

75. 75
square wave generator

76. 76
Multivibrator
Multivibratorsareagroupofregenerativecircuits
thatareusedextensivelyintimingapplications.Itisa
waveshapingcircuitwhichgivessymmetricor
asymmetricsquareoutput.Ithastwostateseither
stableorquasi-stabledependingonthetypeof
multivibrator

77. 77
Monostable multivibrator
Monostablemultivibratorisonewhichgeneratesa
singlepulseofspecifieddurationinresponsetoeach
externaltriggersignal.Ithasonlyonestablestate.
Applicationofatriggercausesachangetothequasi-
stablestate.Anexternaltriggersignalgenerateddueto
charginganddischargingofthecapacitorproducesthe
transitiontotheoriginalstablestate

78. 78
Astable multivibrator
Astablemultivibratorisafreerunningoscillator
havingtwoquasi-stablestates.Thus,thereis
oscillationsbetweenthesetwostatesandnoexternal
signalarerequiredtoproducethechangeinstate

79. 79
Astable multivibrator
Bistablemultivibratorisonethatmaintainsagiven
outputvoltagelevelunlessanexternaltriggerisapplied.
Applicationofanexternaltriggersignalcausesachange
ofstate,andthisoutputlevelismaintainedindefinitely
untilansecondtriggerisapplied.Thus,itrequirestwo
externaltriggersbeforeitreturnstoitsinitialstate

80. 80
Bistable multivibrator
Bistablemultivibratorisonethatmaintainsagiven
outputvoltagelevelunlessanexternaltriggerisapplied.
Applicationofanexternaltriggersignalcausesachange
ofstate,andthisoutputlevelismaintainedindefinitely
untilansecondtriggerisapplied.Thus,itrequirestwo
externaltriggersbeforeitreturnstoitsinitialstate

81. 81
Astable Multivibrator or Relaxation
Oscillator
Circuit Output waveform

82. 82
Equations for Astable Multivibrator21
2
21
2
;
RR
RV
V
RR
RV
V
sat
LT
sat
UT





 








1
21
21
2
ln2
R
RR
ttT 
Assuming
|+V
sat| = |-V
sat|
If R
2is chosen to be 0.86R
1, then T = 2R
fC and
where
= R
fCCR
f
f
2
1


83. 83
Monostable (One-Shot) Multivibrator
Circuit Waveforms

84. 84
Notes on Monostable Multivibrator
•Stable state: v
o= +V
sat, V
C= 0.6 V
•Transition to timing state: apply a -ve input pulse
such that |V
ip| > |V
UT|; v
o= -V
sat. Best to select
R
iC
i0.1R
fC.
•Timing state: C charges negatively from 0.6 V
through R
f. Width of timing pulse is:










LTsat
sat
fp
VV
V
CRt
||
6.0||
ln
Recovery state:v
o= +V
sat; circuit is not ready for retriggering
until V
C= 0.6 V. The recovery timet
p. To speed up the
recovery time, R
D(= 0.1R
f) & C
Dcan be added.
If we pick R
2= R
1/5, then t
p= R
fC/5.

85. 85
Filter
Filterisafrequencyselectivecircuitthatpasses
signalofspecifiedBandoffrequenciesandattenuates
thesignalsoffrequenciesoutsidetheband
Type of Filter
1.Passivefilters
2.Activefilters

86. 86
Passive filters
Passivefiltersworkswellforhighfrequencies.
Butataudiofrequencies,theinductorsbecome
problematic,astheybecomelarge,heavyand
expensive.Forlowfrequencyapplications,morenumber
ofturnsofwiremustbeusedwhichinturnaddsto
theseriesresistancedegradinginductor’sperformance
ie,lowQ,resultinginhighpowerdissipation

87. 87
Active filters
Activefiltersusedop-ampastheactive
elementandresistorsandcapacitorsaspassive
elements.Byenclosingacapacitorinthefeedbackloop
,inductorlessactivefilterscanbeobtained

88. 88
some commonly used active filters
1.Lowpassfilter
2.Highpassfilter
3.Bandpassfilter
4.Bandrejectfilter

89. 89
Classification of ADCs
1.Flash(comparator)typeconverter
2.Countertypeconverter
3.Trackingorservoconverter.
4.Successiveapproximationtype
converter
1.DirecttypeADC.
2.IntegratingtypeADC
Direct type ADCs

90. 90
Integrating type converters
AnADCconverterthatperformconversionin
anindirectmannerbyfirstchangingtheanalog
I/Psignaltoalinearfunctionoftimeorfrequency
andthentoadigitalcodeisknown as
integratingtypeA/Dconverter

91. 91
Sample and hold circuit
Asampleandholdcircuitisonewhich
samplesaninputsignalandholdsontoitslast
sampledvalueuntiltheinputissampledagain.
Thiscircuitismainlyusedindigitalinterfacing,
analogtodigitalsystems,andpulsecode
modulationsystems.

92. 92
Sample and hold circuit
Thetimeduringwhichthevoltageacrossthe
capacitorinsampleandholdcircuitisequalto
theinputvoltageiscalledsampleperiod.The
timeperiodduringwhichthevoltageacrossthe
capacitorisheldconstantiscalledholdperiod

93. 93
UNIT-IV
Special ICs

94. 94
555 IC
The555timerisanintegratedcircuit
specificallydesignedtoperform signal
generationandtimingfunctions.

95. 95
Features of 555 Timer Basic blocks
.1.Ithastwobasicoperatingmodes:monostable
andastable
2.Itisavailableinthreepackages.8pinmetalcan,
8pindip,14pindip.
3.Ithasveryhightemperaturestability

96. 96
Applications of 555 Timer
.
1.astablemultivibrator
2.monostablemultivibrator
3.Missingpulsedetector
4.Linearrampgenerator
5.Frequencydivider
6.Pulsewidthmodulation
7.FSKgenerator
8.Pulsepositionmodulator
9.Schmitttrigger

97. 97
Astable multivibrator
.

98. 98
Astable multivibrator
.
Whenthevoltageonthecapacitorreaches(2/3)Vcc,
aswitchisclosedatpin7andthecapacitoris
dischargedto(1/3)Vcc,atwhichtimetheswitchis
openedandthecyclestartsover

99. 99
Monostable multivibrator
.

100. 100
Voltage controlled oscillator
Avoltagecontrolledoscillatorisanoscillator
circuitinwhichthefrequencyofoscillationscanbe
controlledbyanexternallyappliedvoltage
The features of 566 VCO
1.Widesupplyvoltagerange(10-24V)
2.Verylinearmodulationcharacteristics
3.Hightemperaturestability

101. 101
Phase Lock Looped
APLLisabasicallyaclosedloopsystem
designedtolockoutputfrequencyandphasetothe
frequencyandphaseofaninputsignal
1.Frequencymultiplier
2.Frequencysynthesizer
3.FMdetector
Applications of 565 PLL

102. 102
Active Filters
•Active filters use op-amp(s) and RC components.
•Advantages over passive filters:
–op-amp(s) provide gain and overcome circuit losses
–increase input impedance to minimize circuit loading
–higher output power
–sharp cutoff characteristics can be produced simply
and efficiently without bulky inductors
•Single-chip universal filters (e.g. switched-capacitor
ones) are available that can be configured for any type of
filter or response.

103. 103
Review of Filter Types & Responses
•4 major types of filters: low-pass, high-pass, band pass,
and band-reject or band-stop
•0 dB attenuation in the passband (usually)
•3 dB attenuation at the criticalor cutoff frequency, f
c(for
Butterworth filter)
•Roll-off at 20 dB/dec (or 6 dB/oct) per pole outside the
passband (# of poles = # of reactive elements).
Attenuation at any frequency, f, is:dec
c
fatdBattenx
f
f
fatdBatten )(.log)(.










104. 104
Review of Filters (cont’d)
•Bandwidth of a filter: BW = f
cu-f
cl
•Phase shift: 45
o
/pole at f
c; 90
o
/pole at >> f
c
•4 types of filter responses are commonly used:
–Butterworth -maximally flat in passband; highly non-
linear phase response with frequecny
–Bessel -gentle roll-off; linear phase shift with freq.
–Chebyshev -steep initial roll-off with ripples in
passband
–Cauer (or elliptic) -steepest roll-off of the four types
but has ripples in the passband and in the stopband

105. 105
Frequency Response of Filters
f
A(dB)
f
c
f
A(dB)
HPF
f
clf
cu
f
A(dB)
BPF
f
cl f
cu
f
A(dB)
BRF
f
c
f
A(dB)
LPF
Pass-
band
Butterworth
Bessel
Chebyshev

106. 106
Unity-Gain Low-Pass Filter Circuits
2-pole 3-pole
4-pole

107. 107
Design Procedure for Unity-Gain LPF
Determine/select number of poles required.
Calculate the frequency scaling constant, K
f= 2pf
Divide normalized C values (from table) by K
fto obtain
frequency-scaled C values.
Select a desired value for one of the frequency-scaled C
values and calculate the impedance scaling factor:valueCdesired
valueCscaledfrequency
K
x


Divide all frequency-scaled C values by K
x
Set R = K
xW

108. 108
An Example
Design a unity-gain LP Butterworth filter with a critical
frequency of 5 kHz and an attenuation of at least 38 dB
at 15 kHz.
The attenuation at 15 kHz is 38 dB
the attenuation at 1 decade (50 kHz) = 79.64 dB.
We require a filter with a roll-off of at least 4 poles.
K
f= 31,416 rad/s. Let’s pick C
1= 0.01 mF (or 10 nF). Then
C
2= 8.54 nF, C
3= 24.15 nF, and C
4= 3.53 nF.
Pick standard values of 8.2 nF, 22 nF, and 3.3 nF.
K
x= 3,444
Make all R = 3.6 kW(standard value)

109. 109
Unity-Gain High-Pass Filter Circuits
2-pole 3-pole
4-pole

110. 110
Design Procedure for Unity-Gain HPF
•The same procedure as for LP filters is used except for
step #3, the normalized C value of 1 F is divided by K
f.
Then pick a desired value for C, such as 0.001 mF to 0.1
mF, to calculate K
x. (Note that all capacitors have the
same value).
•For step #6, multiply all normalized R values (from table)
by K
x.
E.g. Design a unity-gain Butterworth HPF with a critical
frequency of 1 kHz, and a roll-off of 55 dB/dec. (Ans.: C
= 0.01 mF, R
1= 4.49 kW, R
2= 11.43 kW, R
3= 78.64 kW.;
pick standard values of 4.3 kW, 11 kW, and 75 kW).

111. 111
Equal-Component Filter Design
2-pole LPF 2-pole HPF
Select C (e.g. 0.01 mF), then:Cf
R
op2
1

A
vfor # of poles is given in
a table and is the same for
LP and HP filter design.1
I
F
v
R
R
A
Same value R & same value C
are used in filter.

112. 112
Example
Design an equal-component LPF with a critical
frequency of 3 kHz and a roll-off of 20 dB/oct.
Minimum # of poles = 4
Choose C = 0.01 mF; R = 5.3 kW
From table, A
v1= 1.1523, and A
v2= 2.2346.
Choose R
I1= R
I2= 10 kW; then R
F1= 1.5 kW, and R
F2=
12.3 kW.
Select standard values: 5.1 kW, 1.5 kW, and 12 kW.

113. 113
Bandpass and Band-Rejection Filter
f
ctr f
ctr
f
cu f
cuf
cl f
cl
f f
Attenuation (dB) Attenuation (dB)
The quality factor, Q, of a filter is given by:BW
f
Q
ctr

where BW = f
cu-f
clandclcuctr fff
BPF BRF

114. 114
More On Bandpass Filter
If BW and f
centreare given, then:24
;
24
2
2
2
2
BW
f
BW
f
BW
f
BW
f
ctrcuctrcl

A broadbandBPF can be obtained by combining a LPF and a HPF:
The Q of
this filter
is usually
> 1.

115. 115
Broadband Band-Reject Filter
A LPF and a HPF can also be combined to give a broadband
BRF:
2-pole band-reject filter

116. 116
Narrow-band Bandpass FilterCRQ
f
BW
ctr
1
2
1
p
 12
2
1
3


Q
R
R
R
2= 2 R
13
1
1
1
22
1
R
R
CR
f
ctr 
p
R
3can be adjusted or trimmed
to change f
ctrwithout affecting
the BW. Note that Q < 1.
C1 = C2 = C

117. 117
Narrow-band Band-Reject Filter
Easily obtained by combining the inverting output of a
narrow-band BRF and the original signal:
The equations for R1, R2, R3, C1, and C2 are the same as before.
R
I= R
Ffor unity gain and is often chosen to be >> R1.

118. 118
UNIT-V
APPLICATION ICs

119. 119
IC Voltage Regulators
•There are basically two kinds of IC voltage regulators:
–Multipin type, e.g. LM723C
–3-pin type, e.g. 78/79XX
•Multipin regulators are less popular but they provide the
greatest flexibility and produce the highest quality
voltage regulation
•3-pin types make regulator circuit design simple

120. 120
Multipin IC Voltage Regulator
LM 723C Schematic
•The LM723 has an
equivalent circuit that
contains most of the parts
of the op-amp voltage
regulator discussed
earlier.
•It has an internal voltage
reference, error amplifier,
pass transistor, and
current limiter all in one
IC package.

121. 121
LM723 Voltage Regulator
•Can be either 14-pin DIP or 10-pin TO-100 can
•May be used for either +ve or -ve, variable or fixed
regulated voltage output
•Using the internal reference (7.15 V), it can operate as a
high-voltage regulator with output from 7.15 V to about
37 V, or as a low-voltage regulator from 2 V to 7.15 V
•Max. output current with heat sink is 150 mA
•Dropout voltage is 3 V (i.e. V
CC> V
o(max)+ 3)

122. 122
LM723 in High-Voltage Configuration
External pass transistor and
current sensing added.
Design equations:2
21
)(
R
RRV
V
ref
o

 21
21
3
RR
RR
R

 m ax
7.0
I
R
sens

Choose R
1+ R
2= 10 kW,
and C
c= 100 pF.
To make V
ovariable,
replace R
1with a pot.

123. 123
LM723 in Low-Voltage Configuration
With external pass transistor
and foldback current limitingse ns5
54o4
(m a x)L
RR
)RR(7.0VR
I

 se ns5
54
short
RR
)RR(7.0
I

 (m a x)Loshort
o
se ns
I7.0)7.0V(I
V7.0
R

 L4se ns5
54L
o
RRRR
)RR(R7.0
'V



Under foldback condition:21
re f2
o
RR
VR
V



124. 124
Three-Terminal Fixed Voltage Regulators
•Less flexible, but simple to use
•Come in standard TO-3 (20 W) or TO-220 (15 W)
transistor packages
•78/79XX series regulators are commonly available with
5, 6, 8, 12, 15, 18, or 24 V output
•Max. output current with heat sink is 1 A
•Built-in thermal shutdown protection
•3-V dropout voltage; max. input of 37 V
•Regulators with lower dropout, higher in/output, and
better regulation are available.

125. 125
Basic Circuits With 78/79XX Regulators
•Both the 78XX and 79XX regulators can be used to
provide +ve or -ve output voltages
•C
1and C
2are generally optional. C
1is used to cancel
any inductance present, and C
2improves the transient
response. If used, they should preferably be either 1 mF
tantalum type or 0.1 mF mica type capacitors.

126. 126
Dual-Polarity Output with 78/79XX
Regulators

127. 127
78XX Regulator with Pass Transistor
•Q
1starts to conduct when
V
R2= 0.7 V.
•R2 is typically chosen so
that max. I
R2 is 0.1 A.
•Power dissipation of Q
1is
P = (V
i-V
o)I
L.
•Q
2is for current limiting
protection. It conducts
when V
R1= 0.7 V.
•Q
2must be able to pass
max. 1 A; but note that
max. V
CE2is only 1.4 V.m ax
1
7.0
I
R 2
2
7.0
R
I
R

128. 128
78XX Floating Regulator
•It is used to obtain an
output > the V
reg
value up to a max.of
37 V.
•R
1is chosen so that
R
10.1 V
reg/I
Q,
where I
Qis the
quiescent currentof
the regulator.2
1
RI
R
V
VV
Q
reg
rego 







 1
1
2
)(
RIV
VVR
R
Qreg
rego



or

129. 129
3-Terminal Variable Regulator
•The floating regulator could be made into a variable
regulator by replacing R
2with a pot. However, there are
several disadvantages:
–Minimum output voltage is V
reginstead of 0 V.
–I
Qis relatively large and varies from chip to chip.
–Power dissipation in R
2can in some cases be quite
large resulting in bulky and expensive equipment.
•A variety of 3-terminal variable regulators are available,
e.g. LM317 (for +ve output) or LM 337 (for -ve output).

130. 130
Basic LM317 Variable Regulator Circuits
Circuit with capacitors
to improve performance
Circuit with protective
diodes
(a) (b)

131. 131
Notes on Basic LM317 Circuits
•The function of C
1and C
2is similar to those used in the
78/79XX fixed regulators.
•C
3is used to improve ripple rejection.
•Protective diodes in circuit (b) are required for high-
current/high-voltage applications.2
1
RI
R
V
VV
adj
ref
refo 








where V
ref= 1.25 V, and I
adjis
the current flowing into the adj.
terminal (typically 50 mA).1
1
2
)(
RIV
VVR
R
adjref
refo



R
1= V
ref/I
L(min), where I
L(min)
is typically 10 mA.

132. 132
LM317 Regulator Circuits
Circuit with pass transistor
and current limiting
Circuit to give 0V min.
output voltage

133. 133
Block Diagram of Switch-Mode Regulator
It converts an unregulated dc input to a regulated dc
output. Switching regulators are often referred to as
dc to dc converters.

134. 134
Comparing Switch-Mode to Linear
Regulators
Advantages:
–70-90% efficiency (about double that of linear ones)
–can make output voltage > input voltage, if desired
–can invert the input voltage
–considerable weight and size reductions, especially at
high output power
Disadvantages:
–More complex circuitry
–Potential EMI problems unless good shielding, low-
loss ferrite cores and chokes are used

135. 135
General Notes on Switch-Mode Regulator
The duty cycle of the series transistor (power switch) determines
the average dc output of the regulator. A circuit to control the
duty cycle is the pulse-width modulatorshown below:

136. 136
General Notes cont’d . . .
•The error amplifiercompares a sample of the regulator
V
oto an internal V
ref. The difference or error voltage is
amplified and applied to amodulatorwhere it is
compared to a triangle waveform. The result is an
output pulse whose width is proportional to the error
voltage.
•Darlington transistors and TMOS FETs with f
Tof at least
4 MHz are often used. TMOS FETs are more efficient.
•A fast-recovery rectifier, or a Schottky barrier diode
(sometimes referred to as a catch diode) is used to direct
current into the inductor.
•For proper switch-mode operation, current must always
be present in the inductor.

137. 137
ICL8038 Function Generator IC
•Triangle wave at pin10 is
obtained by linear charge
and discharge of C by
two current sources.
•Two comparators trigger
the flip-flop which
provides the square wave
and switches the current
sources.
•Triangle wave becomes
sine wave via the sine
converter .

138. 138
ICL8038 Function Generator IC
•To obtain a square wave output, a pull-up resistor
(typically 10 to 15 kW) must be connected between pin 9
and V
CC.
•Triangle wave has a linearity of 0.1 % or better and an
amplitude of approx. 0.3(V
CC-V
EE).
•Sine wave can be adjusted to a distortion of < 1% with
amplitude of 0.2(V
CC-V
EE). The distortion may vary with f
(from 0.001 Hz to 200 kHz).
•IC can operate from either single supply of 10 to 30 V or
dual supply of 5 to 15 V.

139. 139
ICL8038 Function Generator Circuit
+V
CC> V
sweep> V
total+ V
EE+ 2
where V
total= V
CC+ |V
EE|total
sweepCC
o
VRC
VV
f
1
2
)(3

where R = R
A= R
B
If pin 7 is tied to pin 8,










BA
A
A
o
RR
R
CR
f
2
15
3
1
For 50 % duty cycle,1
3.0
RC
f
o


140. 140
Isolation Amplifier
•Provides a way to link a fixed ground to a floating
ground.
•Isolates the DSP from the high voltage associated with
the power amplifier.

141. 141
ISOLATION AMPLIFIER
Purposes
•Tobreakgroundtopermitincompatiblecircuits
•tobeinterfacedtogetherwhilereducingnoise
•Toamplifysignalswhilepassingonlylow
leakagecurrenttopreventshocktopeopleordamageto
equipment
•Towithstandhighvoltagetoprotectpeople,
circuits,andequipment

142. 142
Methods
•Power Supply Isolation : battery, isolated power
•Signal Isolation : opto-isolation, capacitive

143. 143
OPTOCOUPLER
•Theoptocouplersprovideprotectionandhigh-speed
switching
•Anoptocoupler,alsoknownasanopto-isolator,isan
integralpartoftheoptoelectronicsarena.Ithasfast
provenitsutilityasanelectricalisolatororahigh-speed
switch,andcanbeusedinavarietyofapplications.
•Thebasicdesignforoptocouplersinvolvesuseofan
LEDthatproducesalightsignaltobereceivedbya
photodiodetodetectthesignal.Inthisway,theoutput
currentorcurrentallowedtopasscanbevariedbythe
intensityoflight.

144. 144
OPTOCOUPLER
•AverycommonapplicationfortheoptocouplerisaFAX
machineorMODEM,isolatingthedevicefromthe
telephonelinetopreventthepotentiallydestructivespike
involtagethatwouldaccompanyalightningstrike.This
protectivetoolhasotherusesintheoptoelectronicarea.
ItcanbeusedasaguardagainstEMI,removingground
loopsandreducingnoise.
•Thismakestheoptocoupleridealforuseinswitching
powersupplyandmotorcontrolapplications.Todayas
semiconductorsarebeingdesignedtohandlemoreand
morepower,isolationprotectionhasbecomemore
importantthaneverbefore.

145. 145
Optoelectronic Integrated Circuits
Applications
•Inter-and intra-chip optical interconnect and clock
distribution
•Fiber transceivers
•Intelligent sensors
•Smart pixel array parallel processors

146. 146
Optoelectronic Integrated Circuits
Approaches
•Conventional hybrid assembly: multi-chip modules
•Total monolithic process development
•Modular integration on ICs:
•epitaxy-on-electronics
•flip-chip bump bonding w. substrate removal
•self-assembly

147. 147
LM380 Power Amplifier
General Description
•TheLM380isapoweraudioamplifierforconsumer
application.Inordertoholdsystemcosttoaminimum,
gainisinternallyfixedat34dB.Auniqueinputstage
allowsinputstobegroundreferenced.Theoutputis
automaticallyselfcenteringtoonehalfthesupply
voltage.Theoutputisshortcircuitproofwithinternal
thermallimiting.
•Thepackageoutlineisstandarddual-in-line.Acopper
leadframeisusedwiththecenterthreepinsoneither
sidecomprisingaheatsink.Thismakesthedeviceeasy
touseinstandardp-clayout.

148. 148
Features
•Wide supply voltage range
•Low quiescent power drain
•Voltage gain fixed at 50
•High peak current capability
•Input referenced to GND
•High input impedance
•Low distortion
•Quiescent output voltage is at one-half of the supply
•voltage
•Standard dual-in-line package

149. 149
PIN DIAGRAM AND BLOCK DIAGRAM
OF LM380

150. 150
Circuit Diagram for a Simple LM380-
Based Power Amplifier