EDC

UNIT-2

1) If a resistor is introduced in the emitter of a common-emitter(CE)

amplifier then

(A) both input impedance and voltage gain increases

B) input impedances increases and voltage gain decreases

(C) input impedances decreases and voltage gain increases

(D) both input impedances and voltage gain decreases

Ans. B

Current stability of a CC amplifier can be increased by2)  A) Reducing both emitter and base resistance

B) Increasing both emitter and base resistanceC) Reducing emitter resistance and increasing base resistanceD) Increasing emitter resistance and decreasing base resistance

Ans. A

 

3) Which of the following statements are correct for basic transistor amplifier configuration?

A) CB amplifier has low input impedance and a low current gain B) CC amplifier has low output impedance and a low current gainC) CE amplifier has very poor voltage gain but very high input impedanceD) The current gain of CB amplifier is higher than the current gain of CC

amplifierAns. A

In the BJT amplifier, the transistor is biased in the forward active region putting a capacitor across RE will:

4)

  A) Decrease the voltage gain and decrease the input impedance

B) Increase the voltage gain and decrease the input impedance

C) Decrease the voltage gain and increase the input impedance

D) Increase the voltage gain and increase the input impedance

Ans. C

In a common emitter BJT amplifier, the maximum usable supply voltage is limited by:

5)

  A) Avalanche breakdown of base–emitter junctionB) Collector–base breakdown voltage with emitter open (BVCBO)C) Collector–emitter breakdown voltage with base open (BVCEO)D) Zener breakdown voltage of the emitter -base junction

Ans. B)

Introducing a resistor in the emitter of a common emitter amplifier stabilizes the dc operating point against variations in:

6)

  A) Only the temperature B) Only the β of the transistorC) Both temperature and βD) None of the aboveAns.C

In a CE transistor amplifier, if collector–emitter voltage increases the instantaneous operating point:

7)

  A) Moves up the load lineB) Moves down the load lineC) Moves at right angle to the load lineD) Remains stationaryAns. A

The h-parameter equivalent circuit of a junction transistor is valid for:

8)

  A) High frequency, large signal operationB) High frequency, small signal operationC) Low frequency, small signal operationD) Low frequency, large signal operation

Ans. C

The small signal input impedance of a transistor when the output is shorted for the measuring signal, is: (where the symbols have then usual measuring)

9)

 

Ans. A

 

For obtaining hybrid parameters of a transistor:10)  A) Variable Vbe and Ie are taken as independent variables

B) The two independent variables are the ones that are most easily measurable for a CE configuration

C) Variable ib and vce ie are taken as dependent variablesD) Variable Vbe and ie are taken as dependent variables

Ans: C

The condition necessary to calculate hoe of a transistor:11)  A) DC base current is to be zero

B) Base to emitter voltage is to be constant

C) Collector current is to be constantD) Base current is to be constantAns. D

12)The approximate value of input impedance of a common emitter amplifier with emitter resistance Re is given by:

16)  A)hie + A1Re

B)hie + (1 + hfe) Re

C)hieD)(1 + hfe) Re

Ans.B

13) Which of the following configurations has the lowest output impedance?A.Fixed-biasB.Voltage-dividerC.Emitter-followerD.None of the above

Ans. C

14) Which of the h-parameters corresponds to hre in a common-base configuration?A. hib B.hfb

C.hrb D.hob

Ans. C

15) Refer to this figure. Find the value of IE.

A. 2 mA

B.4 mAC.5 mAD. 6 mA

16) Which of the following is referred to as the reverse transfer voltage ratio?

A. hi B.hr

C.hfD. ho

Ans. B

17) Which of the following conditions must be met to allow the use of the approximate approach in a voltage-divider bias configuration?

A. re > 10R2

B. RE > 10R2

C. RE < 10R2

D re < 10R2

.Ans. B

18) Refer to this figure. Determine the value of Av.

A.49.6 B.5

C.100 D.595

Ans. A

19) For a common-emitter amplifier, the purpose of swamping is

A. to minimize gain.

B.to reduce the effects of r'eC.to maximize gain.D. no purpose.

Ans. C

20)  What is the typical value of the current gain of a common-base configuration?A. Less than 1

B.Between 1 and 50

C.Between 100 and 200D. Undefined

Ans. A

21) What is the most important r parameter for amplifier analysis?A. rb′ B.rc′

C.re′

Ans. C

22) The ________ model fails to account for the output impedance level of the device and the feedback effect from output to input.

A. hybrid equivalent

B.re

C.D. Thevenin

Ans. C

23) Refer to this figure. Calculate the value of VB.

A. 5 V

B.3.7 V

C. 20 V

D. 3 V

Ans. B

24) You have a need to apply an amplifier with a very high power gain. Which of the following would you choose?A. common-collector B.common-base

C.common-emitter D.emitter-follower

 

Ans. C

25) What is the voltage gain of a feedback pair connection?A. 1 B.–1

C.100 D.–100Ans. A

26) A common-emitter amplifier has ________ voltage gain, ________ current gain, ________ power gain, and ________ input impedance.A. high, low, high, low

B.high, high, high, lowC.high, high, high, high

D low, low, low, high

Ans. C

27) What is the range of the input impedance of a common-base configuration?A. A few ohms to a maximum of 50

B.1 k to 5 kC.100 k to 500 kD. 1 M to 2 M

Ans. C

28) What is the typical range of the output impedance of a common-emitter configuration?A.10 to 100B.1 k to 5 kC.40 k to 50 kD.500 k to 1 M

Ans. B

29) What is the unit of the parameter ho?A. Volt

B.OhmC.SiemenD. No unit

Ans. C

30) Refer to this figure. Calculate the value of Rin(tot).

A. 37.7 k

B.3.77 kC.378 D 2.25 k

.Ans. B

31) What is the range of the current gain for BJT transistor amplifiers?A.less than 1B.1 to 100C.above 100

D.All of the above

Ans. D

32) What does the negative sign in the voltage gain of the common-emitter fixed-bias configuration indicate?A.The output and input voltages are 180º out of phase.B.Gain is smaller than 1.C.Gain is larger than 1.D.None of the above

Ans. A

33) For the common-emitter fixed-bias configuration, there is a ________ phase shift between the input and output signals.A.0º B.45ºC.90º D.180º

Ans. D

34) Which one of the following configurations has the lowest input impedance?A. Fixed-bias B.Common-base

C.Emitter-follower D.Voltage-divider?Ans. B

35) The differential amplifier hasA one input and one output.

.B.two inputs and two outputs.C.two inputs and one output.D. one input and two outputs.

Ans. C

36) The emitter-follower configuration has a ________ impedance at the input and a ________ impedance at the output.A. low, low

B.low, highC.high, lowD. high, high

Ans. C

37) The differential amplifier produces outputs that areA. common mode.

B.in-phase with the input voltages.C.the sum of the two input voltages.D. the difference of the two input voltages.

Ans. D

38) The ________ model suffers from being limited to a particular set of operating conditions if it is to be considered accurate.A.hybrid equivalentB.re

C.D.Thevenin

Ans. A

 

39) The ________ configuration is frequently used for impedance matching.A fixed-bias

.B.voltage-divider biasC.emitter-followerD. collector feedback

Ans. C

40) Refer to this figure. You notice while servicing this amplifier that the output signal at Vout is reduced from normal. The problem could be caused by

A.an open C3.B.an open C2.C.an open base-emitter of Q2.D.a shorted C2.

Ans. B

41) When the bypass capacitor is removed from a common-emitter amplifier, the voltage gainA.increases.B.decreases.C.has very little effect.D. None of the aboveAns.B

52) Refer to this figure. Determine the value of VC.

A.20 VB.10 VC.5 VD.0 VAns. c

53). In a common-base amplifier, the input signal is connected to theA. base. B.collector.

C.emitter. D. output.

Ans. C

54) Which of the following is (are) true to achieve a good overall voltage gain for the circuit?A. The effect of Rs and RL must be considered as a product.

B.The effect of Rs and RL must be considered as a product and evaluated individually.

C.The effect of Rs and RL must be evaluated individually.D. None of the above

Ans. B

55) To analyze the common-emitter amplifier, what must be done to determine the dc equivalent circuit?A. leave circuit unchanged

B.replace coupling and bypass capacitors with opensC.replace coupling and bypass capacitors with shortsD. replace VCC with ground

Ans. B

56) For the common-emitter amplifier ac equivalent circuit, all capacitors areA. effectively shorts.

B.effectively open circuits.C.not connected to ground.D. connected to ground.

Ans. A

58) Under which of the following conditions is the output impedance of the network approximately equal to RC for a common-emitter fixed-bias configuration?A. ro 10RC

B.ro < 10RC

C.ro < ro

D. ro > ro

Ans. A

59). Which of the following gains is less than 1 for a common-base configuration?A.Ai

B.Av

C.Ap

D.None of the aboveAns. A

60) Which of the following define(s) the conversion efficiency?A.Ac power to the load/ac input powerB.Ac power to the load/dc power suppliedC.Dc output power/ac input powerD.All of the above

Ans. D

61) Which of the following should be done to obtain the ac equivalent of a network?A. Set all dc sources to zero

B.Replace all capacitors by a short-circuit equivalent.C.Remove all elements bypassed by the short-circuit equivalent.

D All of the aboveAns. D

62) In an unbypassed emitter bias configuration hie replaces ________ in the re model.A. re

B.C. re

D. Ib

Ans. C

63) Which of the following is (are) true regarding the input impedance

for frequencies in the midrange 100 kHz of a BJT transistor amplifier?A.The input impedance is purely resistive.B.It varies from a few ohms to megohms.

C.An ohmmeter cannot be used to measure the small-signal ac input impedance.

D.All of the aboveAns. D

64) For the collector dc feedback configuration, there is a ________

phase shift between the input and output signals.A.0º B.45ºC.90º D.180º

Ans. D

65) A common-collector amplifier has ________ input resistance, ________ current gain, and ________ voltage gain.A. high, high, low

B.high, low, lowC.high, low, high

Ans. A

66) The total gain of a multistage amplifier is the ________.A. sum of individual voltage gains

B.sum of dB voltage gains

Ans. B

67) Which of the following configurations has an output impedance Zo equal to RC?A.Fixed-bias common-emitterB.Common-emitter voltage-divider with bypass capacitorC.Common-emitter voltage-divider without bypass capacitorD.All of the above

Ans. D

69). For a common-emitter amplifier, the purpose of the emitter bypass capacitor isA.no purpose, since it is shorted out by RE.B.to reduce noise.C.to despike the supply voltage.

D.to maximize amplifier gain.Ans. D

70) For BJT amplifiers, the ________ gain typically ranges from a level just less than 1 to a level that may exceed 1000.A.VoltageB.CurrentC.ImpedanceD.All of the above

Ans. B

71) Which of the following configurations has a voltage gain of –RC /re?A. Fixed-bias common-emitter

B.Common-emitter voltage-divider with bypass capacitorC.Fixed-bias common-emitter and voltage-divider with bypass capacitorD. Common-emitter voltage-divider without bypass capacitor

Ans. D

72) An emitter-follower amplifier has an input impedance of 107 k . The input signal is 12 mV. The approximate output voltage is (common-collector)A.8.92 VB.112 mVC.12 mVD.8.9 mV

Ans. C

73) Refer to this figure. The output signal from the first stage of this amplifier is 0 V. The trouble could be caused by

A. an open C4.

B.an open C2.C.an open base-emitter of Q1.D. a shorted C4.

Ans C

74) What is the limit of the efficiency defined by = Po / Pi?A.Greater than 1B.Less than 1C.Always 1D.None of the above

Ans. B

75) What is Beta equal to in terms of h parameters?A.hre

B. hoe

C.hie

D hfe

Ans. D

76) What is the controlling current in a common-base configuration?A. Ie

B.Ic

C.Ib

D. None of the above

Ans. A

77) Which of the following techniques can be used in the sinusoidal ac analysis of transistor networks?A. Small-signal

B.Large-signalC.Small- or large-signalD. None of the above

Ans. A

78) The input impedance of a BJT amplifier is purely ________ in nature and can vary from a few ________ to ________.A. resistive, ohms, megohms

B.capacitive, microfarads, faradsC.inductive, millihenrys, henrysD. None of the above

Ans. A

79) The ________ the source resistance and/or ________ the load resistance, the less the overall gain of an amplifier.A. smaller, smaller

B.smaller, largerC.larger, smallerD. larger, larger

Ans. C

80) Refer to this figure. If an emitter bypass capacitor was installed, what would the new Av be?

A.4.96 B.125

C.398 D. 600

Ans. B

81) Which of the following statements is true for hybrid model and re model for a transistor amplifier? (A) re model is limited to a particular set of operating conditions while hybrid model works for the whole region of operation. (B) Hybrid model is limited to a particular set of operating conditions while re model works for the whole region of operation. (C) Both models are exactly the same. (D) None of the above. Ans. C

82) While drawing the ac equivalent model for a BJT amplifier, (A) All the capacitors and DC sources are open circuited. (B) All the capacitors and DC sources are short circuited. (C) Capacitors are short circuited and DC sources are open circuited. (D) Capacitors are open circuited and DC sources are short circuited.

Ans. B

83) For an ac equivalent model of CE Fixed Bias configuration (A) Input and output impedances are approximately equal. (B) Input Impedance is large as compared to the output impedance. (C) Input impedance is small as compared to the output impedance. (D) None of the above. Ans. B

84) For ac equivalent models of CE Fixed bias and CE voltage divider bias, reducing ro? (A) Causes an increase in Zo, Av and Ai. (B) Causes a decrease in Zo, Av and Ai. (C) Has no effect on Zo, Av and Ai. (D) None of the above.Ans. B

85) To isolate the dc analysis from the ac analysis of transistor small signal amplifier (A) Superposition theorem is used because transistor small signal amplifiers are considered non- linear. (B) Superposition theorem is used because transistor small signal amplifiers are considered linear. (C) None of the above. Ans. B

86) The ideal maximum voltage gain of a common-collector amplifier is what?(A) infinite(B) zero(C)indeterminate(D)1Ans. D

87) What happens to the gain of an amplifier if negative feedback is added?(A) increases(B)decreases© becomes zero(D) becomes infiniteAns. B

88)A common collector amplifier is best described by which of these?(A) low voltage gain(B) high voltage gain© low input resistance(D) low current gainAns. A

89) What coupling is used in a multi-stage amplifier for amplifying DC signals?(A) direct(B) RC C) R(D) transformerAns. A

90) Which configuration gives the highest power gain?(A) common-base(B) common-emitterC) Common-collector(D) common-groundAns. B

91) Which of the following is not a BJT amplifier configuration?(A) common-base(B) common-sourceC) common-emitter(D) common-collectorAns. B

92) The point of intersection of the DC and AC load lines is called what?(A) cut-off point(B) saturation point(C operating point

(D) common point

Ans. C

93) Compared to the CE and CC amplifier, a CB amplifier exhibits which of the following?(A) lower input resistance(B) larger voltage gain©larger current gain(D) higher input resistanceAns. A

94) What load does a transistor see at zero signal condition?(A) AC(B)DCC) AC and DC(D) ZeroAns. D

95) In the AC equivalent of a transistor amplifier, capacitors are considered as what?(A) short(B) open(C resistive(D) power supplyAns. A

96) What is another name for a common-emitter circuit?A) Grounded emitterB) Grounded baseC) Grounded collectorD) Emitter-followerAns. A

97) A CE amplifier always exhibits what output signal?A) Equal to the input signalB) Greater than the input signalC) out of phase with the input signal

D) In phase with the input signalAns. C

98) Which of the following is an emitter follower circuit?A) common base amplifierB) common emitter amplifierc) common collector amplifierD) differential amplifierAns. C

99) A buffer amplifier helps achieve which of the following?A) minimum loading and maximum mismatchB) minimum loading and minimum mismatchC) maximum loading and minimum mismatchD) maximum loading and maximum mismatchAns. B

100) An emitter follower is often used for what?A) impedance matchingB) voltage amplificationC) current amplificationD) power amplificationAns. A

101) Why must the impedance of the load match the impedance of the amplifier?A) to minimize power transferB) to prevent signal distortionC) to maximize signal to noise ratioD) to maximize power transferAns. D

102) What is the main benefit of cascading amplifiers?A) lower power supplyB) lesser distortionC) longer amplifier lifeD) higher over-all gainAns. D

103) Which of the following has an input impedance that depends strongly on load resistance?A) CBB) CEC) CCD) CDAns. B

104) Which transistor mode gives the inverted output: -

  A) Common Emitter    B) Common Base     C) Common Collector   D) None of theseAns. A

105) Which coupling gives the higher gain in case of amplifier: -  A) Capacitor coupling    B) Impedance coupling C) Transformer couplingAns. A

106) The important characteristic of emitter-follower is(A) high input impedance and high output impedance(B) high input impedance and low output impedance(C) low input impedance and low output impedance(D) low input impedance and high output impedanceAns. B

107) The common collector amplifier is also known as(A) collector follower (B) Base follower(C) Emitter follower (D) Source followerAns: C

108) In class–A amplifier, the output current flows for(A) a part of the cycle or the input signal.(B) the full cycle of the input signal.

(C) half the cycle of the input signal.(D) 3/4th of the cycle of the input signal.Ans.:- B

109) In an amplifier with negative feedback(A) only the gain of the amplifier is affected(B) only the gain and bandwidth of the amplifier are affected(C) only the input and output impedances are affected(D) All of the four parameters mentioned above would be affectedAns.:- D

110) If the Q of a single-stage single-turned amplifier is doubled, then its bandwidth will

(A) remain same (B) become half(C) become double (D) become four timesAns. B