part 8-elec buk(final)

8/11/2019 PART 8-Elec Buk(Final)

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PART 8 TRANSISTORS and AMPLIFIERS

I. TRANSISTOR FUNDAMENTALS

TRANSISTOR Developed in December 23,1947 in Bell laboratories

By John Bardeen, William Shockley and Walter Brattain

Basically a resistor that ampliies electrical imp!lses as they are transerred

rom its inp!t to its o!tp!t terminals"

Basic Types

1. BIPOLAR JUNCTION TRANSISTOR (BJT) #t is a three layer semicond!ctor device consistin$ o either t%o & and one '(

type layers o materials or t%o ' and one &(type layers o semicond!ctor materials"

T!ee !e"i#ns #$ BJTa" Base

)e$ion to %hich carriers lo% rom emitter to collector

1*17 dopants+cm3

oderately doped

b" -mitter )e$ion rom %hich carriers lo%

1*

19

dopants+cm

3

.eavily doped

c" /ollector )e$ion to %hich carriers lo%

1*10 dopants+cm3

i$htly doped

ar$est

BJT S%!&c%&!e and C#ns%!&c%i#n

Mac!# In%e"!a%ed T!ainin" and Re'ie Cen%e! E*c+!,ni-

Dry/ell



/0 Transistors and Amplifiers

T!ansis%#! C&!!en%s and C#n$i"&!a%i#ns a" /ommon Base /oni$!ration

#n this circ!it, the inp!t si$nal is applied at the emitter, the o!tp!t is taken at the

collector and the base is the common terminal his has very lo% inp!t impedance

Apa ( ) #n the dc mode the levels o #/ and #- d!e to maority carriers are related by a !antity

called alpha and deined by the ollo%in$ e!ation5

e

c

I

I

b" /ommon -mitter /oni$!ration he inp!t is applied at the base, the ampliied o!tp!t is taken rom the

collector, and the emitter is the common terminal" his circ!it is the one $enerally !sed or transistors beca!se the /- ampliier

has the best combination o c!rrent and volta$e $ains

E*c+!,ni- Mac!# In%e"!a%ed T!ainin" and Re'ie Cen%e!



Transistors and Amplifiers - 2

Ie c3 II

Be%a (β) )atio o the collector c!rrent to the base c!rrent

β =3

c

I

I

c" /ommon /ollector /oni$!ration his circ!it has the inp!t applied at the base, the o!tp!t taken at the emitter

terminal and the collector is the common terminal #mpedance matchin$

4a55a (δ

) 6or%ard c!rrent $ain or common collector coni$!ration

δ

3

e

I

I

C#5pa!is#n #$ A5pi$ie! C#n$i"&!a%i#ns

Ca!ac%e!is%ic C#55#n

Base

C#55#n

E5i%%e!

C#55#n

C#ec%#! P#e! 4ain moderate hi$hest moderate6#%a"e 4ain hi$hest moderate less than 1C&!!en% 4ain lo%est less

than1moderate hi$hest





Inp&%I5pedance

lo%est moderate hi$hest

O&%p&%I5pedance

hi$hest moderate lo%est

PaseIn'e!si#n

none 1*8 !t o phase none

Appica%i#ns )6 amp !niversal isolation

T!ansis%#! Biasin" Bias

an electrical, mechanical, or ma$netic orce applied to a device to establish a

desired electrical or mechanical reerence level or its operation" is a D/ volta$e or c!rrent that sets the operatin$ point or ampliyin$ the :/

si$nal

a" 6i;ed Bias is taken rom a battery or po%er s!pply

b" Sel Bias he ampliier prod!ces its o%n D/ volta$e rom an #) drop across a resistor in

the ret!rn circ!it o the common terminal" Sel(bias is probably the type o bias !sed most oten beca!se it is economical

and has stabili<in$ eect on the D/ level o the o!tp!t c!rrent" /an be emitter stabili<ed or collector stabili<ed





c" =olta$e(Divider Bias he most stable type o circ!it biasin$

d" Si$nal Bias





Re"i#ns #$ T!ansis%#! Ac%i#n

a" :ctive )e$ion Base(emitter !nction is or%ard biased and the collector(base !nction is

reverse biased" ransistor>s active operation as an ampliier

b" Sat!ration )e$ion both !nctions are or%ard biased

s%itch on operation or the transistor

c" /!t o )e$ion

both !nctions are reverse biased s%itch o operation or the transistor

L#adine and :/p#in%




Transistors and Amplifiers - ;

L#adine is a strai$ht line dra%n on the collector c!rves bet%een the c!t(o

and sat!ration points o the transistor :/p#in% ?@!iescent 'ointA is the operatin$ point o the transistor %ith the time

varyin$ so!rces o!t o the circ!it

Re'ie :&es%i#n< iven the circ!it belo%, dra% the D/ loadline

:nalysis5 :t c!t(o, #c C * th!s =/- C =//

:t sat!ration, =/- C * th!s #c C =// + )c

BJT S5a Si"na Anaysis

=/Pa!a5e%e!s<




/ Transistors and Amplifiers

1" hi ( short circ!it inp!t impedance

Ii

6ii

=

(6# >)

2" hr ( open circ!it reverse volta$e $ain ?volta$e eedback ratioA

! 6#

6i (Ii >)

3" h ( short circ!it or%ard c!rrent $ain

$ Ii

I# ( 6# >)

4" ho ( open circ!it o!tp!t admittance

# 6#

I# (Ii >)

0. FIELD EFFECT TRANSISTOR (FET) Unipolar device beca!se they operate only %ith one type o char$e carrier

Voltage controlled device %here the volta$e bet%een t%o o the terminals

?$ate and so!rceA controls the c!rrent thro!$h the device" aor eat!re is very high input resistance

a. J&nc%i#n Fied E$$ec% T!ansis%#! (JFET) perates %ith a reverse(biased '& !nction to control c!rrent in the channel

S!are la% device beca!se o the relation o #D and =S




Transistors and Amplifiers - ?

ID C

0

)#$$ (4S

4SDSS6

61I

J6-+D(S6- transer characteristics /an be n(channel or p(channel

JFET Sy53#s

Ope!a%i#n #$ JFET J6- is al%ays operated %ith the $ate(so!rce '& !nction reversed biased

)everse biasin$ o the $ate(so!rce !nction %ith ne$ative volta$e prod!ces a

depletion re$ion alon$ the '& !nction %hich e;tends into the n(channel andth!s increases its resistance by restrictin$ the channel %idth as sho%n in theprecedin$ i$!re"




/1> Transistors and Amplifiers

DC Biasin" $#! JFET 1" 6i;ed Bias

a separate po%er so!rce"

2" Sel Bias





3" So!rce Bias

4" =olta$e Divider

3. Me%a O@ide Se5ic#nd&c%#! Fied E$$ec% T!ansis%#! (MOSFET)





second cate$ory o the ield eect transistor

beca!se o the presence o an ins!lated $ate then it is sometimes called

#6-s S6-S diers rom J6- in that it has no '& !nction str!ct!re

#t has t%o basic types, D ES6- and - E S6-

Depe%i#n MOSFET (D/MOSFET) he drain and so!rce are di!sed into the s!bstrate material and connected by

a narro% channel adacent to the ins!lated $ate #t can be operated in t%o modes(the depletion mode or the enhancement mode

and sometimes called depletion+enhancement mode S6- #t can be operated %ith a <ero, positive or ne$ative $ate(so!rce volta$e

&ormally operated in the depletion mode

When coni$!red as s%itch, it is normally(on

Depe%i#n M#de &e$ative $ate to so!rce volta$e is applied

n Echannel is depleted o some electrons hence decreasin$ channel

cond!ctivity

Enance5en% M#de positive $ate volta$e is applied

more cond!ction electrons are attracted to the channel th!s enhancin$ channel

cond!ctivity





Enance5en% MOSFET (E/MOSFET)

operates only in the enhancement mode has no depletion mode

it has no str!ct!ral channel

it has no #DSS parameter

or an n(channel type o this device, a positive $ate volta$e above threshold

ind!ces a channel by creatin$ a layer o ne$ative char$es ?inversion layerA inthe s!bstrate portion that is adacent to the Si2 layer"

:n n(channel -(S6- has a positive =S %hile a p(channel -(S6- has

a ne$ative =S

he cond!ctivity o its channel is enhanced by increasin$ the $ate to so!rce

volta$e 6or $ate volta$e belo% the threshold, there is no channel to be ormed

# coni$!red as a s%itch, this device is normally o

LD MOSEFT, VMOSFET and TMOSFET are -S6- technolo$iesdeveloped or hi$her po%er dissipation





II. AMPLIFIERS

-lectronic devices capable o ampliication or increasin$ the amplit!de o

po%er, c!rrent or volta$e at its o!tp!t /irc!its desi$ned to increase the amplit!de or level o an electronic si$nal"

Fsed as boosters

Cassi$ica%i#ns #$ A5pi$ie!s< 1. Acc#!din" %# F&nc%i#n

a"=olta$e :mpliier =olta$e controlled so!rce

p(amps are volta$e ampliier

b"/!rrent :mpliier /!rrent controlled so!rce

BJs are c!rrent ampliier

c"'o%er :mpliier Boost the po%er level o the si$nal

0. Acc#!din" %# C#n$i"&!a%i#n a" /ommon Base :mpliier

ransistor ampliier %here inp!t is applied at the emitter and o!tp!t is taken

rom the collector terminal he base is common to both inp!t and o!tp!t

a;im!m c!rrent $ain is 1

&o phase inversion rom inp!t to o!tp!t

b" /ommon /ollector :mpliier ?emitter ollo%erA ransistor ampliier %here inp!t is applied at the base, o!tp!t is taken rom the

emitter terminal a;im!m volta$e $ain is 1

/apacitors m!st have a ne$li$ible reactance at the re!ency o operation

&o phase inversion rom inp!t to o!tp!t

c" /ommon -mitter :mpliier





ransistor ampliier %herein the inp!t is applied at the base and the o!tp!t is

taken rom the collector terminal here is a phase inversion rom inp!t to o!tp!t

2. Acc#!din" %# Cass #$ Ope!a%i#n a" /lass : :mpliier b" /lass B :mpliier c" /lass / :mpliier d" /lass :B :mpliier

Cass A Cass B Cass C Cass AB

E$$iciency 0*G 7"0G 1**G Bet%een :H B

C#nd&c%i#nAn"e

3I*° 1*° Belo%

1*°

Sli$htly$reater

than 1*°

Dis%#!%i#n o% .i$h e;treme moderate

Bias(3ase e5i%%e!)

inear portion

:bovec!t(o

Belo%c!t(o

c!t(o

inp!t o!tp!t

o!tp!t o!tp!to!tp!to!tp!t

C#5pa!is#n #$ A5pi$ie! Casses

7. Acc#!din" %# F!e&ency a" D/ :mpliier

:mpliies D/ si$nal?<ero re!encyA

b" :!dio :mpliier :mpliies si$nal %hose re!ency is %ithin the a!dio ran$e?2* .<(2*.<A

c" )6 :mpliier :mpliies si$nal %hose re!ency is %ithin the radio re!ency ran$e

d" #6 :mpliier

:mpliies si$nal %hose re!ency is in bet%een the carrier and the mod!latin$re!ency e" =ideo :mpliier

: %ide(band ampliier that ampliies video si$nal





=ideo si$nal reers to the re!ency ran$e o the pict!re inormation %hich

arises rom the television scannin$ process

8. Acc#!din" %# %e Si"na 3ein" a5pi$ied a" Small Si$nal :mpliiers

:mpliier that !tili<es only the very linear portion o the active device

b" ar$e Si$nal :mpliiers :mpliier that !tili<es almost the !ll rated o!tp!t po%er o the active device

9. Acc#!din" %# Me%#d #$ C#&pin" a" Direct /o!plin$

:mpliiers connected or co!pled %itho!t any passive component in bet%een"

b" /apacitive /o!plin$ :mpliiers are connected or co!pled by the !sed o capacitor termed as

co!plin$(capacitor

c" #nd!ctive /o!plin$ :mpliiers are connected or co!pled by the !se o ind!ctor or transormer

d" ransormer /o!plin$ ost oten, ind!ctor is not !sed as co!plin$ device instead transormer is !sed

;. P#e! A5pi$ie!s a" '!sh('!ll :mpliiers

:mpliier %ith t%o similar circ!its operatin$ in phase opposition"

ne ampliies hal o the cycle and the remainin$ hal is bein$ ampliied by the

other ampliier

b" /omplementary ESymmetry :mpliiers '!sh(p!ll ampliiers !sin$ complementary transistors s!ch as pair o pnp and

npn

c" @!asi(/omplementary :mpliier '!sh(p!ll ampliiers !sin$ the same transistors at the o!tp!t b!t the driver is

!sin$ complementary transistors




Transistors and Amplifiers - 1;

C#5p#&nd C#n$i"&!a%i#ns a" /ascade /onnection

a cascade connection is a series connection %ith the o!tp!t o one sta$e then

applied as inp!t to the second sta$e" he cascade connection provides a m!ltiplication o the $ain o each sta$e or

a lar$er overall $ain"A' A'1A'0A'2.. A'n

A'(dB) 0>#" (A')

b" /ascode /onnection a cascode connection has one transistor on top o ?in series %ithA another

his arran$ement is desi$n to provide hi$h inp!t impedance %ith lo% volta$e

$ain to ens!re that the inp!t iller capacitance is minim!m"

c" Darlin$ton /onnection he main eat!re o the Darlin$ton connection is that the composite transistor

acts a sin$le !nit %ith a c!rrent $ain that is the prod!ct o the c!rrent $ains o the individ!al transistors"

#t is a circ!it meant to boost inp!t resistance

D 1 0

d" 6eedback 'air he eedback pair connection is a t%o(transistor circ!it that operates like the

Darlin$ton circ!it #t !ses a pnp transistor drivin$ an npn"





TEST OURSELF 8 Re'ie :&es%i#ns 1" : '&' transistor is made o

a" siliconb" $ermani!mc" carbond" either silicon or $ermani!m

Anse! d" either silicon or $ermani!m

2" he transistor is !s!ally encaps!lated ina" $raphite po%der b" enamel paintc" epo;y raisind" black plastic

Anse! c" epo;y raisin

3" 'o%er transistors are invariably provided %itha" solder connectionsb" heat sinkc" metallic casin$d" scre% bolt

Anse! b" heat sink

4" he transistor speciication n!mber 2& reers to aa" diodeb" !nction transistor c" 6- %ith one $ated" S/)

Anse! b" !nction transistor

0" Which i the ollo%in$ is necessary or a transistor actionKa" the base re$ion m!st be very %ideb" the base re$ion m!st be very narro%c"the base re$ion m!st be made rom ins!latin$ materials

d" the collector re$ion m!st be heavily doped

Anse! b" the base re$ion m!st be very narro%

I" :s compared to a /B ampliier a /- ampliier has




Transistors and Amplifiers - 1?

a" lo% c!rrent ampliication

b" hi$her c!rrent ampliicationc"lo%er inp!t resistanced" hi$her inp!t resistance

Anse! b" hi$her c!rrent ampliication

7" #t is the most stable type o circ!it biasin$a" sel(biasb" si$nal biasc" volta$e(divider biasd" i;ed bias

Anse! c" volta$e(divider bias

" he !iescent state o a transistor implies

a" <ero biasb" no o!tp!tc" no distortiond" no inp!t si$nal

Anse! d" no inp!t si$nal

9" -ach o the 2 cascaded sta$es has a volta$e $ain o 3*" What is the overall $ainKa"3b" 9c" 3*d" 9**

Anse! d" 9**S#&%i#n

total C ?3*A?3*A C 9**

1*" Which class o ampliiers operates %ith the least distortionKa"/lass :b" /lass Bc" /lass /d" /lass D

Anse! a" /lass :

11" Which o the ollo%in$ circ!it is the astest s%itchin$ deviceKa" J6-b" BJc" S6-d" riode

Anse! c" S6-

12" Which o the ollo%in$ device is a !nipolarKa" 6-




/0> Transistors and Amplifiers

b" BJc" Lener diode

d" -D

Anse! a" 6-

13" he cascaded ampliier %hich is oten !sed in the #/ isa" ind!ctively co!pledb" capacitively co!pledc" direct co!pledd" transormer co!pled

Anse! c" direct co!pled

14" .i$hest operatin$ re!ency can be e;pected in case o a" bipolar transistor b" J6-c" S6-d" #6-

Anse! a" bipolar transistor

10" Which o the ollo%in$ is e;pected to have the hi$hest inp!t impedanceKa" S6-b" J6- ampliier c" /- bipolar transistor d" // bipolar transistor

Anse! a" S6-

1I" he MMMMMMis !ite pop!lar in di$ital circ!its especially in /S %hich re!ire very lo% po%ercons!mption"a" J6-b" BJc" D(type S6-d" -(type S6-

Anse! d" -(type S6-

17" What is the ampliication actor in 6- transistor ampliiersKa" Lib" $mc" #Dd" #

Anse! b" $m

1" he -(S6- is !ite pop!lar in %hat type o applications"a" di$ital circ!itryb" hi$h re!ency





c"b!erin$

d" a, b and c

Anse! d" a, b and c

19" : J6- !st operates %ith speciicallya" the drain connected to $ro!ndb" $ate to so!rce '& !nction or%ard biasedc" $ate connected to the so!rced" $ate to so!rce '& !nction reverse biased

Anse! d" $ate to so!rce '& !nction reverse biased

2*" he main dierence o a S6- rom a J6- is that

a" J6- has '& !nctionb" o the po%er ratin$c" S6-S has t%o $atesd" S6-s do not have physical channel

Anse! a" J6- has '& !nction

21" : small si$nal ampliier a" !ses only a small portion o its loadlineb" al%ays has an o!tp!t si$nal in the m= ran$ec" $oes into sat!ration once on each inp!t cycled" is al%ays a common emitter ampliier

Anse! a" !ses only a small portion o its loadline

22" he parameter he corresponds toa" ND/

b" N :/

c" r>ed" r>c

Anse! b" N :/

23" # the D/ emitter c!rrent in a certain transistor ampliier is 3 m:, the appro;imate val!e o r>e isa" 3Ob" 3Oc" "33 Od" *"33 O

Anse! c" "33 O

S#&%i#n

r>e C Ω= II"7m:3

m=2I





24" he inp!t resistance o a common base ampliier isa" very lo%

b" very hi$hc" the same as /-d" the same as //

Anse! a" very lo%

20" -ach sta$e o a o!r sta$e ampliier has a volta$e $ain o 10" he overall volta$e $ain isa" I*b"10c" 0*I20d" 3*7

Anse! c" 0*I20S#&%i#n

=over(all C ?10A?10A?10A?10A C 0* I20

2I" he ma;im!m eiciency o a transormer co!pled /lass : ampliier isMM"a" 20b" 0*c" 7"0d" 1**

Anse! b" 0*

27" #n a S6-, the process o creatin$ a channel by the addition o char$e carrier is called"a" ind!cementb" improvementc" balancin$d" enhancement

Anse! d" enhancement

2" What is the c!rrent $ain o a common base circ!it calledKa" $ammab" deltac" bravod" alpha

Anse! d" alpha

29" he name o the very irst transistor a" diodeb" !nction transistor c" point contact transistor

d" triode

Anse! c" point contact transistor

3*" )e$ion in a transistor that is heavily doped"





a" collector

b" emitter c" based" $ate

Anse! b" emitter

31" #n a common Ebase ampliier the volta$e $ain isMMMMM"?:pril, 2**3Aa" medi!mb" lo%c" <erod" hi$h

Anse! d" hi$h

32" #n a common collector ampliier, the inp!t resistance isMMM"?&ov,2**3Aa" hi$hb" <eroc" medi!md" lo%

Anse! a" hi$h

33" : depletion S6- ?D(S6-A can operate %ith %hich o the ollo%in$ $ate(so!rcevolta$eK ?&ovember, 2**3A1" <ero2" positive3" ne$ative

a" 1 onlyb" 2 only

c" 3 onlyd" 1, 2 and 3

Anse! b" 3 only

34" What problem is ca!sed by a loosely co!pled transormer in an )6 ampliierK ?:pril, 2**4Aa" a too narro% bandpassb" over co!plin$c" optim!m co!plin$d" a too(%ide bandpass

Anse! a" a too narro% bandpass

30" &ormally, ho% are hi$h po%er t!bes testedK ?:pril, 2**4Aa" vis!allyb" individ!allyc" in their circ!itd" !se portable testers

Anse! c" in their circ!it


part 8-elec buk(final)

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