RVS COLLEGE OF ENGINEERING AND TECHNOLOGY

DEPARTMENT OF ECE
EC2254-LINEAR INTERGATED CIRCUITS
Two Mark qu!"#o$! w#"% A$!wr!&
UNIT ' I
1. What is a current mirror?
A current mirror consists of two transistors Q
1
and Q
2
such that bases and
emitters of Q
1
and Q
2
are tied together to have same V
BE
. The transistor Q
1
act as a diode
by shorting its base with the coector termina. !n"ut current of !
ref
fows through Q
1
.
#ince Q
2
is identica to Q
1
$ emitter current of Q
2
wi be e%ua to Q1& i.e. !
ref
'. As ong as
Q2 is in active region$ !
(2
) !
*
is a refection or mirror of reference current !
ref
and the
circuit is referred to as a current mirror.
2. What is a current re"eater?
The current mirror circuit can be used to source current to more than one
oad. #uch a circuit is caed as a current re"eater.
+. #tate the re%uirements of a good current source?
A good current source shoud meet two re%uirements,
&i' *ut"ut current !
*
shoud be inde"endent of -.
&ii' The out"ut resistance r
o
shoud be very ong.
.. /efine cross over distortion and how it is eiminated?
!n the com"ementary emitter foower out"ut of an *"0am"$ the out"ut votage
Vo remains 1ero unti Vi e2ceeds V
BE
)3.4V. This is caed as cross over distortion.
This can be eiminated by a""ying a bias votage greater than 2 V
BE
) 1V
between the two bases$ so that a sma current fows in the transistors even in the
%uiescent manner.
4. 5ist the reasons for using a eve shifter in an o"0am".
&i' When the *"0am" is used to drive the ne2t stage$ no cou"ing ca"acitor is
used. Because of direct cou"ing$ the /c eve rises form stages to stage. The increase in
/( eve tends to shift the o"erating "oint of the ne2t stage. Thus imit of *60am"
votage swing and "roduces out"ut votage distortion. The %uiescent votage of an one
stage is shifted before it is a""ied to ne2t stage.
&ii' The out"ut shoud have a %uiescent votage eve of 3V for 1ero in"ut signa.
7. E2"ain about in"ut bias current.
!n the differentia am"ifier "resent at the *60am"8s in"ut$ the in"ut transistors
must be biased to the inear regions by su""ying current to the bases by the e2terna
circuits. The bias current !B is the average vaue of the base currents entering into the
terminas of an *"0am".
2
+
+
=
B B
B
I I
I .
9. /efine in"ut offset votages.
The votage re%uired to be a""ied at the in"ut for ma:ing out"ut votage to 1ero
vots is caed as in"ut offset votage.
;. <ow can you muti"y the in"ut offset votages?
A 13= *hms "otentiometer shoud be "aced across offset nu "ins 1 and 4 $ and
the wi"er be connected to the negative su""y "in .. The "osition of the wi"er is ad>usted
to nuify the out"ut offset votage.
?. E2"ain about therma /rift.
Bias current$ offset current and offset votage changes with tem"erature. (hange
in the offset vaues for each degree (esius change in tem"erature is caed as therma
drift.
13. /efine corner fre%uency.
The fre%uency at which the gain is + db ess than the /( vaue of o"en oo" gain
A
*5
is caed as a corner fre%uency.
11. #tate the stabiity criteria of an *"0am".
1 = A
and
= A
12. (assify the ty"es of fre%uency com"ensating techni%ues used in an *"0am".
Two ty"es of fre%uency com"ensating techni%ues are
i' E2terna com"ensation
ii' !nterna com"ensation .
1+. (om"are domain 1ero and "oe01ero com"ensation.
The dominant "oe is seected so that the com"ensated transfer function goes
through 3dB at the first "oe f
1
of the uncom"ensated system. !n "oe01ero com"ensation$
the 1ero is chosen at f
1
and "oe is seected so that the modified transfer function goes
through 3dB at the second "oe f
2
of the uncom"ensated system.
1.. /efine sew rate. What causes the sew rate?
The sew rate is defied as the ma2imum rate of change of out"ut votage caused
by the ste" in"ut votage and is s"ecified as Vots "er micro0seconds.
A ca"acitor within or outside the *"0am" "revents the out"ut votage from
res"onding immediatey to a fast changing in"ut and causes sew rate.
14. <ow is the sew rate measured?
#ew rate is measured in Vots "er micro0seconds.
UNIT ' II
1. What are 5inear and non0inear circuits. @ive e2am"es.
!n inear circuits$ the out"ut signa varies with the in"ut signa in inear manner.
E2am"es are adder$ subtractor$ V to ! and ! to V converters.
!n non0inear circuits the in"ut0out"ut characteristics are non0inear. E2am"es are
Aectifiers$ (i""er and 5og am"ifier.
2. #tate the out"ut votage e%uation of an adder and subtractor.
The out"ut votage e%uation of an adder and subtractor with four in"ut votages
V
1
$ V
2
$ V
+
$ and V
.
is$


( ) ( )
2 1 . +
V V V V V
O
+ + =
+. What is a "recision diode. @ive its advantages.
A "recision diode is ca"abe of rectifying votages even before the cut in votage
of an ordinary diode. !t is therefore ca"abe of rectifying the signas of the order of
miivots.
.. E2"ain the roe of a tem"erature sensitive resistor A
T(
in a 5og am"ifier.
The out"ut votage V
*
of the og am"ifier is de"endent u"on the tem"erature and
is directy "ro"ortiona to one. Thia is com"ensated by an *"0am" stage which "rovides a
non0inverting gain of

+
TC
R
R
2
1
. The TC
R
is a tem"erature sensitive resistance with a
"ositive coefficient of tem"erature . so that the so"e of the out"ut votage e%uation
becomes constant as the tem"erature changes.

+ =
ref
i
TC
O
V
V
q
KT
R
R
COM
V n 1
' &
2
4. What are the characteristics of an ide *"0am"?
The characteristics of an ide *"0am" are$
1' *"en oo" votage @ain A
*5
) B
2' !n"ut im"edance A
i
) B
+' *ut"ut im"edance A
*
) 3
.' Bandwidth BW ) B
4' Cero offset . That is V
3
)3 when V
1
)V
2
)3.
7. /raw the 6in diagram of !( 9.1.
Dot connected
V
E
*ut"ut
*ffset nu
*ffset nu
!nverting in"ut
Don F invertg
in"ut
V
0
1 ;

2 9
+ 7
. 4
9. @ive the conditions for sustained osciation.
The conditions for sustained osciations are$
1' Gagnitude condition
1 = A
and
2' 6hase condition
3 3
+73 3 or A = .
;. /efine a com"arator and draw the characteristics of an ide com"arator.
A com"arator is circuit which com"ares a signa a""ied at the in"ut of an *60
am" with a :nown reference votage at the other in"ut. The characteristics of an ide
com"arator are
?. Gention the a""ication of a com"arator.
The various a""ication of com"arators are$
1. Cero crossing detector
2. Window detector
+. Time mar:er generator
.. "hase meter.
13. E2"ain about <ysterisis or Bac:ash.
An abru"t transition between the e2treme vaue of out"ut votage resuts in an
out"ut waveform virtuay discontinuous at the com"arison votage. The circuit is then
said to e2its a "henomenon caed <ysterisis or Bac:ash.
11. Why is a Gonostabe mutivibrator is caed as a 1' Time deay circuit 2'@ating
circuit.
A Gonostabe mutivibrator is caed as a 1' time deay circuit because it generate
a fast transition at a "redetermined time T after the a""ication of in"ut trigger.
A Gonostabe mutivibrator is caed as a 2' gating circuit as it generates a
rectanguar waveform at a definite time which coud be used to gate "arts of a system.
12. Write the e2"ressions for fre%uency of osciation for an A( "hase shift osciator and
Wein bridge osciator.
The e2"ressions for fre%uency of osciation for an A( "hase shift osciator is
RC
f
O

=
72
1
and the e2"ressions for fre%uency of osciation for an wein bridge
osciator is
RC
f
O

=
2
1
EVsat
3
0Vsat
V
i
0 V
ref
1+. /efine <ysterisis width.
<ysterisis width is the difference between the two threshod votages V
HT
and V
5T
and it is given by V
<
) V
HT
0 V
5T
)
2 1
2
2
R R
R
Sat
V
+
.
Where$ V
<
) <ysterisis width
V
HT
)H""er threshod votage
V
5T
)5ower threshod votage
V
#at
)#aturation votage
1.. E2"ain how a non0symmetrica s%uare wave can be obtained.
!n an astabe mutivibrator $ an asymmetric s%uare wave can be get by connecting
two Cener diodes with different brea:down votages V
C1
and V
C2
bac: to bac: at the
out"ut stage.
14. What is a window detector?
A window detector is a circuit which is used to mar: the instant at which an
un:nown in"ut is between two threshod detectors.
17. E2"ain how to measure the "hase differences between two signas.
A sine wave of in"ut fre%uency
T
f
1
=
shoud be a""ied to the in"ut of he
schmitt trigger. A asymmetrica s%uare wave can be obtained. The "hase difference is
measured by $

=

m
UT
V
V
Sin
1

.
Where V
HT
)H""er threshod votage
V
m
)6ea: sinusoida votage
19. Dame a com"arator with "ositive feedbac:.
#chmitt trigger &or' Aegenerative com"arator is a com"arator with "ositive
feedbac:.
1;. 5ist the features of an instrumentation am"ifier.
1' <igh gain accuracy
2' <igh (GAA
+'<igh gain stabiity with ow tem"erature co0efficient
.' 5ow /( offset
4' 5ow out"ut im"edance.
1?. What are active fiters?
Active fiters are circuits which use *60am" as active eements and Aesistor and
(a"acitor as "assive eements.
23. 5ist the advantages of an active fiter over "assive fiter.
i' Active fiters don8t use !nductors.
ii'#ince *"0am"s are used in non0inverting mode configuration$ the ow out"ut
im"edance wi im"rove the oad drive ca"acity. The oad is se"arated from fre%uency
determining networ:.
iii' The vaues of ca"acitances can be reduced by using arge vaues of
resistances because of high in"ut im"edance of *60am".
21. /efine Votage Transfer Iunction.
Votage Transfer Iunction is defined as
' &
' &
' &
s V
s V
s H
i
O
=
. Where$
V
*
&s' ) 5a"ace transform of out"ut votage in time domain.
V
i
&s' ) 5a"ace transform of in"ut votage in time domain.
22. /raw a #aen F=ey fiter.
A #aen F =ey fiter is a genera second order fiter.
2+. /efine Quaity factor Q.
Quaity factor or Iigure of merit is defined as
l h
O O
f f
f
W
f
Q

= =
.
Where$ f
o
) (orner fre%uency
I
h
) u""er cut0off fre%uency
I

) u""er cut0off fre%uency

2.. @ive the two ty"es of B6Is.
i' Darrow band "ass fiter &QJ13'.
ii' Wide band "ass fiter &QK13'.
Af
L1
L2
L
+
L .
Ai
V
i
V
o
UNIT ' III
1. Dame the basic buiding boc: of a 655?
The basic buiding boc: of a 655 are
a' 6hase detector M com"arator b' 5ow "ass fiter
c' Error am"ifier d' Votage controed am"ifier
2. What are the three stages of o"eration of a 655?
The three stages of o"eration of a 655 are
a' Iree running range b' (a"ture range
c' 5oc:ed or trac:ing range
+. /efine 5oc:0in range$ "u0in range and ca"ture range.
Lo(k-#$ ra$)* The range of fre%uencies over which the 655 can maintain oc: with an
in"ut signa is caed as the 5oc:0in range.
Pu++-#$ ra$)* The range of fre%uencies over which the 655 can ac%uire oc: with an
in"ut signa is caed as the "u0in range.
Ca,"ur ra$)* The tota time ta:en by the 655 to estabish oc: is caed as ca"ture
range.
.. Why is a votage controed osciator caed so?
The amount of fre%uency deviation is directy "ro"ortiona to the /( contro
votage and hence it is caed as Votage (ontroed *sciator
4. 5ist the "robems associated with the switch ty"e anaog "hase detector.
The two "robems associated with the switch ty"e anaog "hase detector are
i' The out"ut votage Vo is "ro"ortiona to the in"ut signa am"itude Vs. This is
undesirabe since it ma:es the "hase detector gain and the oo" gain de"endent on the
in"ut signa am"itude.
ii' The out"ut is "ro"ortiona to cosN and not N "ro"ortiona to ma:ing it non0inear.
7. /efine votage to fre%uency conversion factor.
The votage to fre%uency conversion factor =V is defined as$
C
O
V
V
f
K

=
.
Where$
C
V
) Goduation votage re%uired to "roduce the fre%uency shift
O
f
for
the V(*.
9. /raw the "in diagram of DEM#E 474.
1 ;

2 9
+ 7
. 4
EVcc
(
T
A
T
Goduation out"ut
@round
D(
#%uare wave !M6
Trianguar
wave *M6
;. 5ist the a""ications of 655.
The a""ications of 655 are
a' Ire%uency muti"ier b' Ire%uency divider
c' AG demoduator d' IG demoduator and
e' I#= demoduator
?. /raw the characteristics showing the ca"ture range and 5oc:0in range of a 655.
13. What are anaog muti"ier?
An anaog muti"ier acce"ts two in"uts V2 and Vy and "roduces an out"ut
votage Vo which is "ro"ortiona to the "roduct of two in"ut votages. That is
Vo ) = V2 Vy. Where$ =) #cae factor$
1
13
1

V
.
11. Dame a few a""ications of anaog muti"ier.
The muti"iers are used in a'votage divider b'#%uaring circuit
c' #%uare rooting circuit d' 6hase detector e' Ire%uency doubers
f' Aectifier g' AG# detector
12. What is a Trans0conductance muti"ier?
Trans0conductance muti"ier is a votage in"ut $ current out"ut muti"ier whose
out"ut e%uation is given by

=
T E
L
Y !
V R
R
V V V
.
1+. What is a four0%uadrant muti"ier?
A muti"ier that acce"t in"ut of either "oarity and "reserve the correct "oarity
reationshi" at the out"ut is referred to as a four0%uadrant muti"ier.
1.. What shoud be the "hase difference between the in"ut signa and V(* out"ut to
active oc:?
The in"ut signa and V(* signa shoud be ?3 degree out of "hase with each
other to achieve an active oc: condition.
2fc ) ca"ture range
2f5 ) oc: range
&OM2'=PA
0&OM2'=PA
Vc
fs
fo0Qf5 fo0Qfc
foEQfc
foEQf5
fo
14. What are the ty"es of "hase detector.
The ty"es of "hase detector are anaog "hase detector and digita "hase detector.
17. @ive e2am"es for digita "hase detector.
The e2am"es of digita "hase detectors are E2cusive *A "hase detector$ edge
"hase detector and monoithic "hase detector.
19. What is the range of moduating signa a""ied to the V(*?
The range of moduating signa a""ied to the V(* is 3.94Vcc to Vcc.
1;. @ive the "ur"ose of the com"ounding "rocess.
The "rocess of com"ounding is a combination of com"ressing and e2"anding.
The "ur"ose of com"ounding is to "reserve the signa to noise ratio of the origina signa
and to avoid non inear distortion of the signa.
UNIT ' IV
1. Which is the fastest A/( and why?
The fastest ty"e of A/( is the "arae com"arator of fash ty"e A/( as the
conversions for a the bit "ositions ta:es "ace simutaneousy.
2. 5ist the various cassifications of A/(8s.
A/(8s are cassified into two grou"s namey /irect ty"e A/(8s and !ntegrating ty"e
A/(8s.
E2am"es of /irect ty"e A/(8s incudes i' Iash ty"e A/( ii' (ounter ty"e A/(
iii'Trac:ing or #ervo ty"e A/( and iv' successive a""ro2imation ty"e A/(.
E2am"es of !ntegrating ty"e A/(8s incude i'(harge baancing A/( ii' /ua so"e
A/(.
+. @ive the advantages of fash ty"e A/(8s.
i' The number of com"arator re%uired amost doubes for each added bit.
ii' !i' The arge the number of bits$ the "riority encoder becomes com"e2.
.. What are the integrating ty"es of A/(8s?
!ntegrating ty"e A/( "erforms conversion first by changing the anaog in"ut signa
to a inear function of time or fre%uency and then to a digita code.
4. /efine Aesoution.
The resoution of a converter is the smaest change in votage which may be
"roduced at the out"ut of the converter.
Aesoution in vots ) V
I#
M &2
n
F 1'.
) 1 5#B increment.
7. E2"ain how dua0so"e A/( "rovides noise re>ection.
The dua0so"e A/( integrated the in"ut signa for a fi2ed time$ hence it "rovides a
e2ceent noise re>ection of A c signas whose "eriods are integra muti"es of the
integration time T
1
.
9. 5ist the im"ortant s"ecifications of A/(M/A(.
The im"ortant s"ecifications are$
i' Aesoution
ii' 5inearity
iii' Accuracy
iv' Gonotonicity
v' #etting time
vi' #tabiity.
;. Dame three switches used in A/(8s.
i' #inge "oe doube through ty"e
ii' Totem "oe G*#IET ty"e
iii' (G*# inverter switch.
iv'
?. @ive the two disadvantages of A02A adder /A(.
!n A02A adder /A($ the fowing in the resister change as the in"ut data changes.
Gore "ower dissi"ation causes heating which creates non0inearity in /A(.
13. Why an inverted A02A adder /A( caed so?
The inverted A02A adder /A( is caed so because the "osition of G#B and 5#B are
interchanged when com"ared to A02A adder /A(.
11. 5ist the two advantages of A02A adder /A(.
i' Both the terminas of the switch are at ground "otentia$ current fowing in the
resistances is constant and is inde"endents of the switch "osition.
ii' The stray ca"acitances are not abe to "roduce sow0down effects on the
"erformance of the circuit.
12. Where do we use successive a""ro2imation ty"e of /A(8s?
#uccessive a""ro2imation ty"es of /A(8s are used in a""ications where conversion
s"eed is an im"ortant "arameter. !t is used in data ogger and instrument.
1+. 5ist some sam"e and hod !(8s.
i' <arris semiconductor <A 2.23
ii' Dationa semiconductors such as 5I1?;$ 5I +?; F are used as sam"e and
hod !(8s.
1.. 5ist some a""ications of sam"e and hod circuit.
#am"e and hod circuits are used in a""ications where digita interfacing and anaog
to digita and "use code moduation systems are used.
14. What is a V0I converter?
A V0I converter acce"ts an anaog in"ut V
i
and generates a "use train with fre%uency
f
3
) =Vi. Where = is the votage to fre%uency conversion sensitivity in <1 M Vots.
17. What is a I0V converter?
An I 0V converter acce"ts a "eriodic waveform of fre%uency f
i
and yieds an anaog
out"ut Vo.
V
3
) = f
i
. Where = is the fre%uency to votage conversion sensitivity in <1 M Vots.
UNIT ' V
1. /raw the "in diagram of 444 timer.
2. E2"ain the function of reset.
The Aeset in"ut "in . "rovides a mechanism to reset the II in a manner which
overrides the effect of any instruction coming to II from ower com"arator. This
overrides reset is effective when the reset in"ut is ess than about 3..V. When reset is not
used$ it is returned to Vcc.
+. What are the modes of o"eration of a timer?
The modes of o"eration of timers are Gono0stabe mode and astabe mode.
.. 5ist some a""ications of timer in the mono0stabe mode.
The a""ications of timer in the mono0stabe mode are$
i' Gissing "use detection
ii' !i' 5inear Aam" generator
iii' Ire%uency divider
iv' 6use width moduator
4. /efine duty cyce /.
The duty cyce / of a circuit is defined as the ratio of *D time to the tota time "erid T
and it is given by / ) t
*D
M &t
*D
E t
*II
'.
7. <ow is symmetrica s%uare wave get generated?
The symmetrica s%uare wave generator can be constructed by adding a coc:ed R=
fi"0fo" to the out"ut of the non0symmetrica s%uare wave generator. The coc:ed Ii"0
fo" acts as binary divider to the time out"ut.
9. What is a votage reguator?
A votage reguator is an eectronic circuit that "rovides a stabe /( votage inde"endent
of the oad current$ tem"erature and A( ine votage variations.
1
2
+
.
;
9
7
4
Vcc
/ischarge
Thrreshod
(ontro votage
@round
Trigger
*ut"ut
Aeset
;. /ifferentiate between series and switching reguator.
#eries Aeguator #witching Aeguator
#eries "ass transistor o"erates in the
active region as a inear device.
#eries "ass transistor o"erates either at
cutoff &or' at saturation as a switching
device
6ower dissi"ation is more 6ower dissi"ation is ess
Efficiency is ess Efficiency is more
?. /efine ine reguation.
5ine reguation is defined as the "ercentage change in the out"ut votage for a change
in the in"ut votage.
13. /efine oad reguation.
5oad reguation is defined as the "ercentage change in the out"ut votage for a change
in the oad current.
11. /raw the standard re"resentation of an !( votage reguator.
12. E2"ain current imiting.
(urrent imiting refers to the abiity of a reguator to "revent the oad current from
increasing above a "resent vaue.
1+. E2"ain current Iodbac: characteristics.
As current demand increases$ the out"ut votage is hed constant ti a "resent current
eve is reached. !f the current demand e2ceeds this eve$ both out"ut current and votage
decreases.
1.. <ow current boosting is achieved in !( 92+.
The current eve of the !(92+ reguator can be boosted by adding a boost transistor
Q1 to the votage reguator so that the base current get muti"ied by beta of the "ass
transistor.
14. What is the "rinci"e of switched mode "ower su""y?
#witched mode "ower su""ies rey on "use width moduation to contro the average
vaue of the out"ut votage. The average vaue of the re"etitive "use waveform de"ends
1 ;

2 9
+ 7
. 4
EVcc
(
T
A
T
Goduation out"ut
G(9;SS(
!D *HT
@D/
Hnreguated
!n"ut $ Vin
Aeguated
*ut"ut $ Vo
3.++TI 1TI
1 2
+
on the area under the waveform. !f the duty cyce is varied$ the average vaue of the
votage changes "ro"ery.
17. What is a switched ca"acitor fiter?
A switched ca"acitor fiter is three termina eements which consist of ca"acitor$
"eriodic switches and o"erationa am"ifier and whose o"en circuit votage transfer
function re"resents fitering characteristics.
19. Gention any disadvantages of switched ca"acitor fiter.
i' The A( "roducts are set by the ca"acitor ratio and switch "eriod.
ii' 5arge vaues of A are easiy simuated by the combination of sma vaue
ca"acitor and G*# switching transistors.
1;. 5ist some a""ications of 5G+;3 audio "ower am"ifier.
i' Audio am"ifier
ii' <igh gain audio am"ifier
iii' !ntercom system
1?. What is an isoation am"ifier?
An isoation am"ifier is an am"ifier that offers an ohmic or eectrica insuation between
its in"ut and out"ut terminas.
23. What is an o"to cou"er?
The o"to0cou"er circuit consists of a "hoto emitting device and a "hoto sensing
device. The current fowing through the sensing device is directy "ro"ortiona to the
intensity of ight emitted by the emitting device.