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......................ECECTRONIC CIRCUIT ANALYSIS...........ALL D VERY BEST........VAMSI KRRISH.4 U!!!
1) Critical capacitance with smallest equivalent resistance that determines the lower cut off of CB amplifier is
a) I/P coupling capacitor
b) Emitter bypass capacitor if c1 = c2
c) c2 output coupling capacitor
d) None.
ans: [ a ]
2) Non-linear distortion is maximum in [ b ]
a) class B mode
b) class A mode
c) class AB mode
d) class C mode
ans: [ B ]
3) typical value of rbb of Ge BJT at room temperature of Ie =1.3ma 100 ohms
4) cascade amplifier is 2- transistor combination has [ b ]
a) collector of first transistor is connected to the base of second transistor
b) collector current of first transistor is same as emitter current of second transistor
c) emitter current of first transistor is same as the collector current of the second transistor
d) none
ans: [ B ]
5) resultant phase shift of odd no of CE amplifier stages at mid band frequency is [ b ]
a) 3600
b) 1800
c) 450
d) 900
ans: [ B ]
6) major drawbacks of Darlington transistor pair is [ d ]
a) low current gain compared to single emitter follower
b) dependence of AV on transistor selected condition
c) low i /p impedance compared to single emitter follower
d) dependence of h-parameters on quiescent point.
ans: [ D ]
7) lower cutoff &higher cutoff frequency of rc coupled amplifier are [ d ]
a) both zero
b) both infinity
c) zero & infinity respectively
d) similar to those of CE stage
ans: [ D ]
8) the miller input capacitance in CB AMP IS [ C ]
a) large compared to miller capacitance in CE
b) very large because of +ve voltage gain in CB
c) small because of +ve voltage gain in CB
d) is not negligible compare to other capacitance
ans: [ C ]
9) identify the correct relationship [ d ]
a) f alpha ~ f beta
b) f beta >> f alpha
c) f alpha ~ ft
d) f alpha >> f beta
ans : [ D ]
10) final stage of multistage amplifier is generally [ a ]
a) a pre-amplifier
b) a voltage post amplifier
c) a power amplifier
d) a microphone amplifier
ans: [ A ]
11) Max conversion efficiency of a series fed class A power amplifier is [ d ]
a) 75
b) 100
c) 50
d) 25
ans: [ D ]
12) even harmonics are not present in the o/p of [ d ]
a) class A transformer coupled amplifier
b) class c amplifier
c)class A amplifier
d) class B push pull amplifier
ans: [ D ]
13) voltage gain of an amplifier reduces to 1/(root 2)its max [ b ]
a) break frequency
b) miller frequency
c) half power frequency
d) cutoff frequency
ans: [ B ]
14) Identify the correct statement regarding the voltage gain of a CE transistor amplifier [ a ]
a) it increases with increase in ac load R
b) it is independent of ac load R & is large
c) it decreases with increase in ac load R
d) it is always approximately unity
ans: [ A ]
15) Phase reversal between i/p & o/p signal voltages occurs in [ d ]
a) common base amplifier
b) common drain amplifier
c) common gate amplifier
d) common source amplifier
ans: [ D ]
16) Identify the incorrect statement [ d ]
a) frequency distortion in an amplifier is mainly due to the reactive component circuit
b) amplitude distortion is also referred to as non-linear distortion
c) distortion in amplifier due to unequal phase shifts at different frequencies is called delay distortion
d) phase shift distortion is same as frequency distortion
ans: [D ]
17) Resultant current gain of a Darlington pair individual current gain of hfe is [ d ]
a) hfe/2
b) hfe
c) 2hfe
d) hfe2
ans: [ D ]
18) o/p voltage of a non ideal differential amplifier is [ c ]
a) zero
b) Ad Vd
c) (AdVd+ AcV¬c)
d) AcVc
ans: [ C ]
19) rce >> rbe condition is applicable in hybrid -pie equivalent of CE amplifier because [ a ]
a) collector base junction is reverse biased & emitter base junction is forward biased
b) o/p R is always much larger than i/p R
c) b is the internal base terminal
d) base region is extremely tin compared to emitter & collector terminals
ans: [ A ]
20) expression for short circuit current gain bandwidth [ d ]
a) gm/2pie hfe (ce+cc)
b) gm/(ce+cc)
c) gm/ hfe (ce+cc)
d)gm/2pie (ce+cc)
ans:[ D ]
21) the parameter with 0c/watt as its units of measurement is [ a ]
a) thermal expansion
b) thermal coefficient
c) thermal resistance
d) thermal power
ans : [ A ]
22) Even harmonics in the o/p are connected in push - pull configurations only if [ a ]
a) both transistors are perfectly matched
b) both NPN & PNP transistors are used
c) A phase inversion is not used at inputs of 2 transistors
d) two power supplies are used
ans:[ A ]
23) i/p &o/p capacitors in a transistors amplifier are not referred to as [ a ]
a) inter electrode capacitors
b) coupling capacitors
c) blocking capacitors
d) dc de-coupling capacitors
ans : [ A ]
24) FET amplifier configuration , which is similar to CC BJT is [ b ]
a) common gate amplifier
b) common drain amplifier
c) common source amplifier
d) swamped source resistor amplifier
ans:[ B ]
25) identify the expression for voltage gain CE & fet amplifier at low frequency [ c ]
a) -gm rd Rl /(rd + Rl)
b) gm rd Rl / ( rd +Rl+ gm rd Rl)
c) gm rd Rl /(rd + Rl)
d) Rl || rd / (1+ gm rd)
ans: [ C ]
26) Resultant phase shift of even no of CB amplifier stage at frequency below lower cutoff frequency [ d ]
a) always a multiple of 2 pie
b) product of phase shift introduced by individual stages
c) always 1800
d) sum of the phase shifts introduced by individual stages
ans: [ D ]
27) 2-stage rc coupled amplifier is configured as [ a ]
a) 2 capacitively coupled CE stages cascaded
b) a CE stage capacitively coupled to a CC stage
c) 2 capacitively coupled CB stages cascaded.
d) 2 capacitively coupled CC stages cascaded
ans: [ A ]
28) Identify the incorrect statement for a high frequency hybrid pie model of a BJT is [ a ]
a) high frequency hybrid pie capacitances can be expressed in terms of low frequency h- parameters
b) capacitance between collector & base terminal of a BJT is called overlap -diode capacitance
c) ' B' represent internal base terminal
d) high frequency hybrid pie conductances can be expressed in terms of low frequency h-parameters.
ans:[ A ]
29) identify false statement [ c ]
a) fbeta & Ic exhibits a peak value of a particular ic.
b) unity gain band width Ft is the function of Ic
c)ft & Ic both are functions of f beta
d) Ft variation with Ic is similar to hfe variation with T
ans: [ C ]
30) during the mid band frequency the gain of amplifier is [ d ]
a) 1/(root 2) times Max value
b) min
c)unity
d) constant
ans: [ D ]
31) CB amplifier of BJT is similar in behaviour with following FET configuration [ a ]
a)common gate amplifier
b) common drain amplifier
C) common source amplifier
d)swamped source resistor amplifier
ans:[ A ]
32) 2-transistor cascade with both collectors tied together & emitter of the transistor connected to the base of the transistor is
referred to as [ a]
a) Darlington pair
b) CE &CC cascade
c) cascade amplifier
d) differential pair
ans: [ A ]
33) o/p voltage of an ideal differential amplifier [ b ]
a) zero
b) Ad Vd
c)Ad Vd + AcVc
d) AcVc
ans:[ B ]
34) bandwidth of an amplifier with lower & higher cutoff frequency Fl & Fh .& quantity factor Q is [ a ]
a) Fh - F l
b) Fh/ q
c) (Fh-Fl)/1.414
d) q-Fl
ans: [ A ]
35) identify the expression for voltage gain CD & fet amplifier at low frequency [ b ]
a) -gm rd Rl /(rd + Rl)
b) gm rd Rl / ( rd +Rl+ gm rd Rl)
c) gm rd Rl /(rd + Rl)
d) Rl || rd / (1+ gm rd)
ans: [ B ]
36) the i/p impedance of cascade amplifier is [ b ]
a) hic
b) hie
c) infinity
d) hib
ans: [ B ]
37) the transconductance gm of a transistor depend on [ b ]
a) temperature
b) operation frequency
c) CE voltage
d) C c
ans : [ B ]
38) ft for a ce amplifier is defined as [ b ]
a) the frequency at which the CE current gain falls to half its Max value
b) frequency at which CE current gain becomes unity
c) frequency at which CE voltage gain falls to half its Max value
d) frequency at which CE voltage gain becomes unity
ans: [ B ]
39) the capacitance determining the corner frequency lag network at the i/p of CE amplifier is [ b ]
a) miller i/p capacitor
b) c wiring
c) external capacitor at the base
d)cbe
ans: [ B ]
40) i/p signals swing in class A power amplifier is restricted to [ d ]
a) a small portion around Q point in active region
b) entire portion around Q point in saturation
c) entire portion around Q point in cutoff
d) entire portion around Q point in active
ans: [ D ]
41) transistor in class C amplifier is based beyond cutoff region to [ b ]
a) ensure reduced distortion of o/p signal
b) ensure conduction angle of less than 1800
c) ensure conduction angle of transistor for entire i/p cycle
d) ensure o/p wave shape to the replica of i/p wave shape
ans: [ B ]
42) if Av is the voltage gain of an amplifier in db & Ai is its current gain in db then power gain of amplifier in db is [ d ]
a) Av¬- Ai
b) Av¬/ Ai
c)10log 10 Av¬/ Ai
d) Av+Ai
ans : [ D ]
43) at frequency below lower cut off frequency in CE amplifier coupling capacitor at the base of the amplifier form an LPF [ b ]
a) with emitter resistance
b) with i/p resistance
c) with o/p resistance
d) with base resistance
ans: [ B ]
44) advantage of impedance type inter stage coupling is [ c ]
a) very wide band & frequency independent gain curve
b) flat response of frequency in mid band region
c) no dc voltage drop across collector load
d) no requirement of bulky components all frequency
ans: [ C ]
45) resultant phase shift of odd number of CE amplifier stages at mid band frequency is [ b ]
a) 3600
b)1800
c) 450
d) 900
ans: [ B ]
46) major draw back of Darlington transistor pair [ d ]
a) low current gain compared to single emitter follower
b) dependence of Av on transistor selected
c) low i/p impedance compared to single emitter follower
d) dependence of H -parameters on quiescent conditions
ans: [ D ]
47) lower cutoff & higher cut off frequency of an rc coupled amplifier are [ c ]
a) both zero
b) both infinity
c) similar to of CE stage
d) zero& infinity
ans: [ C ]
48) main characteristic features of differential amplifier is absence of frequency dependent components
49) identify the incorrect statement for a Hybrid pie model of a BJT [ b ]
a) base width modulation due to earlier effect results in variations in collector emitter voltages
b)Hybrid pie model cannot be used for analysis of transistors at high frequencies
c) High frequency hybrid pie conductance can be expressed in terms of low frequency H parameters
d) All the conductances & capacitances of Hybrid pie model are independent of operating frequencies
Ans: [ b ]
50) Frequency of Fbeta = a product of current gain & band width of CE amplifier
51) The miller i/p capacitance in CB amplifier [ c ]
a) Is large compared to miller capacitance in CE
b) is very large because of +ve voltage gain in CB
c) is small because of +ve voltage gain in CB
d) not negligible compared to other capacitance
ans: [ C ]
52) in class A amplifier flow of electric current in terms of i/p signal cycle is for 3600
53) an ideal voltage will have effective o/p impedance = [ b ]
a) no particular value
b)zero
c) always a complex value
d) infinity
ans: [ B ]
54) type of inter stage coupling resulting in highest overall gain [ c ]
a) direct coupling
b)inductive coupling
c) RC coupling
d) transistor coupling
ans : [ C ]
55) main disadvantage of Darlington pair amplifier is [ d ]
a) low i/p impedance
b) low current gain
c) high o/p impedance
d)high leakage current
ans: [ D ]
56) ideal value of CMRR of differential amplifier is [ d ]
a) unity
b) zero
c)100
d) infinity
ans: [ D ]
57) CE is the capacitance of forward biased junction & is therefore [ c ]
a) independent of collector current
b) much lager than Cc
c) mainly diffusion capacitance
d) mainly transition capacitance
ans: [ C ]
58) dissipation capability of a transistor is defined as [ a ]
a) capability to launch heat generated into the surroundings
b) deviation in power delivered to load resistor
c) capability to withstand the variation in dc power at operating power
d) deviation in o/p & i/p signal wave shapes
ans: [ A ]
59) increased conversion efficiency in class B over class A operation is mainly due to [ b ]
a) elimination of all higher harmonics
b) elimination of dc current in the load
c) usage of single power supply
d) elimination of cross over distortion
ans: [ B ]
60) higher cutoff frequency of transistor amplifier is mainly because of [ a ]
a) inter electrode capacitance
b) bypass capacitance
c) blocking capacitance
d ) coupling capacitance
ans: [ A ]
61) phase difference between o/p voltage &i/p voltage of a CC amplifier at mid band frequencies [ b ]
a) 1800
b) 00
c) 450
d) 900
ans : [ B ]
62) phase difference between o/p voltage &i/p voltage of a CG amplifier at mid band frequencies [ b ]
a) 1800
b) 00
c) 450
d) 900
ans : [ B ]
63) audio power amplifiers are also generally referred to as large signal amplifiers
64) ratio of slopes of the gain curve of an amplifier below lower cutoff frequency & above cutoff frequency is [ b ]
a) 3
b) unity
c)2
d) 6
ans: [ B ]
65) the capacitors that are short circuited at low frequencies in CE amplifier are [ d ]
a) o/p coupling capacitors
b) i/p coupling capacitors
c) emitter bypass capacitors
d) inter electrode capacitor
ans:[ B ]
66) the critical capacitance that determines the overall cut off frequency of an amplifier is the one which sees an equivalent resistance [ a ]
a) of minimum value
b) of Max value
c) of infinity value
d) equals to its reactance value at that frequency
ans: [ A ]
67) distortion in amplifiers due to unequal amplitude gains at different frequencies is referred to as [ c ]
a) phase shift distortion
b) amplitude distortion
c) frequency distortion
d) delay distortion
ans : [ C ]
68) slope of the gain curve of an amplifier below cut off frequency is [ a ]
a) -20 db decade
b) 6 db decade
c)-6 db decade
d) 20 db decade
ans : [ A ]
69) the CE short circuit current gain in db at frequency f = Ft is [ d ]
a) hfe/1.414
b) unity
c) hfe
d)zero
ans: [ D ]
70. The frequency at which CE is short circuit current gain becomes unity is represented by__fT_______
71. Non linear distortion is maximum in
a) Class B mode a) Class A mode
a) Class AB mode d) a) Class C mode
Ans: (b)
72. Even harmonics are not present in the o/p of Class B push pull amplifier.
73. Phase difference between o/p and i/p voltages of a transistor amplifier at lower cut off frequencies is
a)180 b) 45 c) 0 d) 90
Ans: (b)
74. All frequencies below lower cut off frequency in a CE amplifier, the coupling capacitor at the base of the amplifier forms a LPF
a)with RE b)Rip c)RB d)Rop
Ans: (b)
75. A CC amplifier is characterized by approximately
A)unity power gain b)unity i/p ,o/p impedance ratio
c)unity voltage gain d) unity current gain
Ans: (c)
76. Voltage gain
of a given CS FET depends on its
a)Dynamic drain resistance b)i/p impedance
c) Amplification factor d)Drain load resistance
Ans: (d)
77. Identify the expression for o/p resistance of a CE amplifier at lower frequencies is
Ans: 1/[ho-hrhf/hi+rs]
78. The type of inter stage coupling used at extremely low frequencies is
a)Inductive coupling b)RC coupling
c) Transformer coupling d) Direct coupling
Ans: (d)
79. Resultant phase shift of even no of CG amplifier stages at higher cut off frequencies is
Ans: Sum of phase shift introduced by individual stages.
80. According to Millers theorem, inter electrode capacitances Ccb for a CE amplifier of gain A results in an miller i/p capacitance of
a) Ccb (A-1)/A b) Ccb A/ (A-1)
c) Ccb (1-A) d) Ccb / (A-1)
Ans: (a)
81. A two transistor combination in CE, CC is not characterized by
a)AI<1>1 c) a)AV<1>> fhout b) fhin<< fhin=" fhout" max =" 0.4">>2kΩ
Ans: (a)
103) The location of operation point of a class A amplifier is
Ans) active region
104) Total harmonic distortion is maximum in
Ans) class C
105) Effect of small value of unbiased emitter resistance in CE amplifier is
(a) Increase in voltage gain at mid band frequency
(b) Decrease in Av at high frequency
(c) Nothing on voltage gain at mid band frequency
(d) Decrease in Av at mid band frequency
Ans: (d)
106) The mid band gain of BJT is 200 and its bandwidth is 1MHz .If circuit parameters are changed such that the gain reduces to 10,the bandwidth coil
(a) remains same (c) also reduces to 1/10th
(c) increases to 20MHz (d) increases to 10 MHz
Ans: (c)
107) Resultant phase shift of five CE emitter amplifier stages cascaded at mid band frequencies is
(a) 360◦ (b) 180◦ (c) 45◦ (d)90◦
Ans: (b)
108) Typical value of gm of Ge BJT at room temperature and Ic=1.3mA is
(a) 50mA/volt (b) 1000Ω (c) 80kΩ (d) 4MΩ
Ans: (a)
109) [hie – gm/hfe] represent hybrid п conductance
(a) Feed back conductance gb′c
(b) Base spreading conductance gbb′
(c) o/p conductance gce
(d) i/p conductance gb′c
Ans: (b)
110) Frequency response of an amplifier is defined as
(a) variation of amplifier frequency as a function
of its voltage gain
(b) variation of magnitude of voltage gain as a
function of phase of the voltage gain
(c) variation of magnitude and phase of voltage
gain with variation in signal frequencies
(d)variation of amplifier frequency as a function of the phase of its voltage gain
Ans: (c)
111) Critical capacitance along the smallest equivalent resistance that determines the lower cut-off frequency of a common drain amplitude is
(a) C1,input coupling capacitor
(b) Cs,source by pass capacitor
(c) Cs,source by pass capacitor ,only if C1=C2
(d) C2,output coupling capacitor
Ans: (d)
112) Resultant upper-cut-off frequency of two identical stages cascaded with individual upper cut-off frequency of 10 KHz is
(a) 6.4 KHz (b) 15.625KHz (c) 10 KHz (d) 5 KHz
Ans: (a)
113) In a two stage BJT cascade amplifier
(a) I/P resistance is comparable with hie of a single
CE stage
(b) O/P resistance is as low as hoe of a single CE
Stage
(c) Reverse voltage gain is much larger than hre of a
Single CE stage
(d) Forward current gain is much smaller than hfe of
Single CE stage
Ans: (c)
114) Typical value of rb′c of Ge BJT at room temper-
-ture and Ic=1.3mA is
(a) 1000Ω (b) 4MΩ (c) 100Ω (d) 80KΩ
Ans: ( b)
115) Identify the conductance that is not included in hybrid п- model
(a) Base emitter conductance, gbe
(b) O/P conductance, gce
(c) Feed back conductance,gb′c
(d) I/P conductance, gb′c
Ans: (a)
116) Class C amplifier find applications in the
following
(a) amp modulation circuits
(b) driving loud speakers
(c) switching devices
(d) comparators
Ans: (a)
117) Mid frequency amplifier range of an amplifier is defined as those frequencies more than 10 times that of lower frequencies and less than 0.1 times that of higher frequency in amplifier does not have any mid frequency range if
(a) fH<100fl>100fL (d) f>100fL
Ans: (a)
118) The mid band voltage gain of an amplifier with band width of 1MHz is 10db,if the circuit components are changed such that the gain becomes 7db ,its bandwidth becomes
(a) 700 KHz (b) 2 MHz (c) 500 KHz (d) 1 MHz
Ans: (b)
119) Resultant voltage gain and phase shift in an n-stage cascaded amplifier with individual gains, A1, A2, A3 …An and phase shifts ө1, ө2 …өn is
(a) Ar=A1.A2.A3……..An and ө=ө1+ө2+……. +өn
(b) Ar=A1.A2…………An and ө=ө1.ө2…………өn
(c) Ar=A1+A2+………+An and ө=ө1.ө2………..өn
(d) Ar=A1+A2+……….+An and ө=ө1+ө2+…….+өn
Ans: (a)
120) Break frequency is the frequency at which the capacitive reactance (Xc) and equivalent resistance (Req) at a point of connection in a circuit have following relation
(a) Xc<
Ans: (c)
121) Basic advantage of DC of amplifier stage is
(a) Ability to provide impedance matching
(b) Ability to provide very small mid band region
(c) Ability to provide narrow and resonant type of frequency response
(d) Ability to amplify DC and very low frequency signal
Ans: (d)
122) Two stage common emitter amplifier configuration with emitters tied together, i/p’s at bases and o/p’s at collectors is called as
(a) Differential pair (b) Cascode amplifier
(c) Boot strap Darlington pair (d) Darlington pair
Ans: (a)
123) Effect of resistor N/W for biasing the
Darlington resistor
Ans) Reduction in overall I/P impedance
124) If a power transistor conducts only during +ve half cycle of i/p signal , the class of operation of the amplifiers is
Ans) Class B
125) Max conversion efficiency of a Class B power amplifier is
Ans) 78.5%
126) If the signal voltages and currents at the i/p of a transistor amplifier are within 1/10th of DC operating point values then transistor is said to be in
(a) small signal mode
(b) low frequency mode
(c) frequency independent mode
(d) DC operating mode
Ans: (a)
127) Phase reversal between O/P and I/P voltages in a CE amplifier occurs at
(a) mid band frequency (b) high cut off frequency
(c) all the frequency (d) lower cut off frequency
Ans: (a)
128) Resonant peak in the frequency response occurs in
(a) DC coupling (b) RC coupling
(c) direct coupling (d) Transformer coupling
Ans: (d)
129. If 2 signals of some amplitude and frequency are applied to a differential amplifier the output is mainly due to the phase difference between the input signals
130. The output conductance gb’e in terms of low frequency h parameter is given by αD / hfe Re .
131. If power transistor conducts for the entire cycle of input signal , the mode of power amplifier is Class A.
132. Identify the incorrect statement with reference to Class B amplifier
Ans: A phase inversion is not required at input in Push Pull Amplifier.
133. Doubling the voltage gain of an amplifier results in increase of voltage gain in dB by 3.01.
134. To obtain a constant and high value of voltage gain at midband frequency in CE Amplifier CE should be large enough such that Xce<
Ans: (a)
103) The location of operation point of a class A amplifier is
Ans) active region
104) Total harmonic distortion is maximum in
Ans) class C
105) Effect of small value of unbiased emitter resistance in CE amplifier is
(e) Increase in voltage gain at mid band frequency
(f) Decrease in Av at high frequency
(g) Nothing on voltage gain at mid band frequency
(h) Decrease in Av at mid band frequency
Ans: (d)
106) The mid band gain of BJT is 200 and its bandwidth is 1MHz .If circuit parameters are changed such that the gain reduces to 10,the bandwidth coil
(a) remains same (c) also reduces to 1/10th
(c) increases to 20MHz (d) increases to 10 MHz
Ans: (c)
107) Resultant phase shift of five CE emitter amplifier stages cascaded at mid band frequencies is
(a) 360◦ (b) 180◦ (c) 45◦ (d)90◦
Ans: (b)
108) Typical value of gm of Ge BJT at room temperature and Ic=1.3mA is
(a) 50mA/volt (b) 1000Ω (c) 80kΩ (d) 4MΩ
Ans: (a)
109) [hie – gm/hfe] represent hybrid п conductance
(e) Feed back conductance gb′c
(f) Base spreading conductance gbb′
(g) o/p conductance gce
(h) i/p conductance gb′c
Ans: (b)
110) Frequency response of an amplifier is defined as
(b) variation of amplifier frequency as a function
of its voltage gain
(b) variation of magnitude of voltage gain as a
function of phase of the voltage gain
(c) variation of magnitude and phase of voltage
gain with variation in signal frequencies
(d)variation of amplifier frequency as a function of the phase of its voltage gain
Ans: (c)
111) Critical capacitance along the smallest equivalent resistance that determines the lower cut-off frequency of a common drain amplitude is
(e) C1,input coupling capacitor
(f) Cs,source by pass capacitor
(g) Cs,source by pass capacitor ,only if C1=C2
(h) C2,output coupling capacitor
Ans: (d)
112) Resultant upper-cut-off frequency of two identical stages cascaded with individual upper cut-off frequency of 10 KHz is
(a) 6.4 KHz (b) 15.625KHz (c) 10 KHz (d) 5 KHz
Ans: (a)
113) In a two stage BJT cascade amplifier
(e) I/P resistance is comparable with hie of a single
CE stage
(f) O/P resistance is as low as hoe of a single CE
Stage
(g) Reverse voltage gain is much larger than hre of a
Single CE stage
(h) Forward current gain is much smaller than hfe of
Single CE stage
Ans: (c)
114) Typical value of rb′c of Ge BJT at room temper-
-ture and Ic=1.3mA is
(a) 1000Ω (b) 4MΩ (c) 100Ω (d) 80KΩ
Ans: ( b)
115) Identify the conductance that is not included in hybrid п- model
(a) Base emitter conductance, gbe
(b) O/P conductance, gce
(c) Feed back conductance,gb′c
(d) I/P conductance, gb′c
Ans: (a)
116) Class C amplifier find applications in the
following
(e) amp modulation circuits
(f) driving loud speakers
(g) switching devices
(h) comparators
Ans: (a)
117) Mid frequency amplifier range of an amplifier is defined as those frequencies more than 10 times that of lower frequencies and less than 0.1 times that of higher frequency in amplifier does not have any mid frequency range if
(a) fH<100fl>100fL (d) f>100fL
Ans: (a)
118) The mid band voltage gain of an amplifier with band width of 1MHz is 10db,if the circuit components are changed such that the gain becomes 7db ,its bandwidth becomes
(a) 700 KHz (b) 2 MHz (c) 500 KHz (d) 1 MHz
Ans: (b)
119) Resultant voltage gain and phase shift in an n-stage cascaded amplifier with individual gains, A1, A2, A3 …An and phase shifts ө1, ө2 …өn is
(a) Ar=A1.A2.A3……..An and ө=ө1+ө2+……. +өn
(b) Ar=A1.A2…………An and ө=ө1.ө2…………өn
(c) Ar=A1+A2+………+An and ө=ө1.ө2………..өn
(d) Ar=A1+A2+……….+An and ө=ө1+ө2+…….+өn
Ans: (a)
120) Break frequency is the frequency at which the capacitive reactance (Xc) and equivalent resistance (Req) at a point of connection in a circuit have following relation
(a) Xc<
Ans: (c)
121) Basic advantage of DC of amplifier stage is
(e) Ability to provide impedance matching
(f) Ability to provide very small mid band region
(g) Ability to provide narrow and resonant type of frequency response
(h) Ability to amplify DC and very low frequency signal
Ans: (d)
122) Two stage common emitter amplifier configuration with emitters tied together, i/p’s at bases and o/p’s at collectors is called as
(a) Differential pair (b) Cascode amplifier
(c) Boot strap Darlington pair (d) Darlington pair
Ans: (a)
123) Effect of resistor N/W for biasing the
Darlington resistor
Ans) Reduction in overall I/P impedance
124) If a power transistor conducts only during +ve half cycle of i/p signal , the class of operation of the amplifiers is
Ans) Class B
125) Max conversion efficiency of a Class B power amplifier is
Ans) 78.5%
126) If the signal voltages and currents at the i/p of a transistor amplifier are within 1/10th of DC operating point values then transistor is said to be in
(e) small signal mode
(f) low frequency mode
(g) frequency independent mode
(h) DC operating mode
Ans: (a)
127) Phase reversal between O/P and I/P voltages in a CE amplifier occurs at
(a) mid band frequency (b) high cut off frequency
(c) all the frequency (d) lower cut off frequency
Ans: (a)
128) Resonant peak in the frequency response occurs in
(a) DC coupling (b) RC coupling
(c) direct coupling (d) Transformer coupling
Ans: (d)
129. If 2 signals of some amplitude and frequency are applied to a differential amplifier the output is mainly due to the phase difference between the input signals
130. The output conductance gb’e in terms of low frequency h parameter is given by αD / hfe Re .
131. If power transistor conducts for the entire cycle of input signal , the mode of power amplifier is Class A.
132. Identify the incorrect statement with reference to Class B amplifier
Ans: A phase inversion is not required at input in Push Pull Amplifier.
133. Doubling the voltage gain of an amplifier results in increase of voltage gain in dB by 3.01.
134. To obtain a constant and high value of voltage gain at midband frequency in CE Amplifier CE should be large enough such that Xce<
135. A differential amplifier cannot be considered as ground input ,single ended output.
136. Cross over distortion in Class B amplifier is due to finite cut-in voltage of 2 transistors.
137. If there are 2 uncoupled high pass filter sections in the equivalent circuit of an amplifier with fL1 and fL2 as cutoff frequency , then the overall lower cutoff frequency of the amplifier approximately is
a) fL2 - fL1
b) smaller of fL2 and fL1
c) fL2 + fL1
d) Larger of fL2 and fL1 , if fL2 and fL1 differ by more than a decade.
Ans: (d)
138. The phase relationship between output and input voltages of a CS amplifier for frequency above higher cut off frequency is
a) both are 180 degrees out of phase
b) output leads input
c) both are in phase
d) output lags input
Ans: (d)
139. According to Millers theorem , the inter-electrode capacitance, Ccb for a CE amplifier of gain A results in a Miller output capacitance of
a) Ccb(A-1)/A b) Ccb A/(A-1) c) Ccb(1-A) d) Ccb /(A-1)
Ans: (a)
140. If V1 = -V2 = 0.5 V are the two input signals applied to a differential amplifier , identify the incorrect statement
a) Common mode voltage is 0
b) Differential mode voltage is 1V
c) Differential mode voltage is 0
d) Output voltage = Differential mode gain
Ans: (c)
141. Gain in dB as a negative number indicates
a) an absolute gain less than 20
b) an absolute gain less than 1
c) an absolute gain less than 0
d) Phase reversal between i/p and o/p
Ans:
142. Crossover distortion in Class B amplifiers can be eliminated by modifying the configuration to Class AB .
143. A voltage gain equal to 0dB of an amplifier corresponds to
a) Power gain of 2
b) Voltage gain of 2
c) Voltage gain of unity
d) Power gain of zero
144. Configuration of transistor amplifier that acts as a buffer for impedance matching is
145. Resultant lower and upper cut off frequency f1n and f2n of an n stage cascaded identical amplifier is
146. A cascode amplifier is a combination of
147. Typical value of Cc of high frequency hybrid ∏ model of a BJT is
148. Resultant upper 3dB frequency of ‘n’ identical upper cut off frequency given as
a) ( f2 )n
b) f2 √(21/n-1)
c) f2 /√(21/n-1)
d) f2
Ans:
149. Base width modulation due to early effect results in variations in collector emitter voltages
150. Input impedance is high and output impedance is low in the following transistor configurations
a) CC b) CB c) CC and CB d) CE
Ans:
151. Identify the correct statement
a) Change in bandwidth for any change in its gain is always 3dB
b) If the gain of an amplifier decreases by 3 dB , its bandwidth remains the same.
c) Gain and bandwidth of an amplifier change such that their product always remains the same.
d) If the gain of an amplifier increases by 3 dB its bandwidth also increases by 3 dB
Ans: (c)
152. Class of operation of power amplifier with transistor conduction for a period much smaller than half cycle input signal is Class C.
153. Class C amplifiers are used as Tuned amplifiers.
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