92 + Interview Questions in Transistor Characteristics in Electronic Devices & Circuits Page 2 InterviewSolution

51.	The disadvantage of using the method of reverse biasing base emitter junction is_________(a) high voltage control signal(b) low voltage control signal(c) output swing(d) incomplete switching of outputThis question was addressed to me in homework.This intriguing question comes from Transistor Switching Times topic in portion Transistor Characteristics of Electronic Devices & Circuits
Answer» Right option is (d) incomplete switching of output Best explanation: This method is used to quickly switch off a transistor is by reverse biasing its base to collector junction. It is DEMONSTRATED in a HIGH voltage switching circuit. The DISADVANTAGE of using the method of reverse biasing base emitter junction is that the output does not switch COMPLETELY to GND due to forward voltage drop of the diode.

Discussion

52.	The DC equivalent circuit for an NPN common base circuit is.I got this question by my college professor while I was bunking the class.My question comes from DC Load Lines in chapter Transistor Characteristics of Electronic Devices & Circuits
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53.	The collector supply voltage for a CE configured transistor is 10V. The resistance RL=800Ω. The voltage drop across RL is 0.8V. Find the value of collector emitter voltage.(a) 3.7V(b) 9.2V(c) 6.5V(d) 9.8VThe question was posed to me in quiz.My doubt is from The Common Emitter Configuration in chapter Transistor Characteristics of Electronic Devices & Circuits
Answer» CORRECT CHOICE is (b) 9.2V The best EXPLANATION: Here, IC=0.8/800=1mA. We KNOW, VCE=VCC-ICRL =10-0.8=9.2V.

Discussion

54.	The current amplification factor ϒdc is given by_________(a) IE/IB(b) IB/IE(c) IC/IE(d) IE/ICI got this question in quiz.Query is from The Common Collector Configuration topic in portion Transistor Characteristics of Electronic Devices & Circuits
Answer» The correct answer is (a) IE/IB The best explanation: When no signal is APPLIED, then the ratio of EMITTER current to base current is called as ϒdc of the transistor.As the collector is common to both input and output circuits, HENCE the NAME common collector configuration.

Discussion

55.	A transistor is connected in CE configuration. Collector supply voltage Vcc=10V, RL=800Ω, voltage drop across RL=0.8V, α=0.96. What is base current?(a) 41.97µA(b) 56.78µA(c) 67.67µA(d) 78.54µAThe question was posed to me in final exam.This intriguing question comes from The Common Emitter Configuration in division Transistor Characteristics of Electronic Devices & Circuits
Answer» CORRECT CHOICE is (a) 41.97µA The EXPLANATION: Here, IC=0.8/800=1mA β= α/ (1-α)=0.96/1-0.96=24. Now, IB=IC/ β=1/24=41.67µA.

Discussion

56.	Which of the following corresponds to the output circuit of a CB transistor?(a) VBE(b) IB(c) VCB(d) VCEThis question was addressed to me in an international level competition.The doubt is from The CB Characteristics in portion Transistor Characteristics of Electronic Devices & Circuits
Answer» RIGHT OPTION is (c) VCB To elaborate: Here, the quantity COLLECTOR to base voltage corresponds to the output circuit of a CB TRANSISTOR. The complete electrical behaviour of a transistor can be described by stating the relation between these QUANTITIES.

Discussion

57.	The output resistance of CB transistor is given by _________(a) ∆VCB/∆IC(b) ∆VBE/∆IB(c) ∆VBE/∆IC(d) ∆VEB/∆IEThis question was addressed to me in an interview.I would like to ask this question from The CB Characteristics topic in chapter Transistor Characteristics of Electronic Devices & Circuits
Answer» The correct CHOICE is (a) ∆VCB/∆IC Easiest EXPLANATION: The ratio of CHANGE in collector base VOLTAGE (∆VCB) to resulting change in collector current (∆IC) at CONSTANT emitter current (IE)¬ is defined as output resistance. This is denoted by ro.

Discussion

58.	Determine the value of emitter current and collector current of a transistor having α=0.98 and collector to base leakage current ICBO=4µA. The base current is 50µA.(a) 1.5mA(b) 3.7mA(c) 2.7mA(d) 4.5mAI have been asked this question in exam.The query is from The Common Base Configuration in chapter Transistor Characteristics of Electronic Devices & Circuits
Answer» The CORRECT ANSWER is (c) 2.7mA The EXPLANATION: Given, IB=50µA=0.05mA ICBO=4µA=0.004Ma IC=α/(1- α)IB+1/(1- α)ICBO=2.45+0.2=2.65Ma IE=IC+IB=2.65+0.05=2.7mA.

Discussion

59.	Which of the following is true in construction of a transistor?(a) the collector dissipates lesser power(b) the emitter supplies minority carriers(c) the collector is made physically larger than the emitter region(d) the collector collects minority charge carriersI had been asked this question in an interview for internship.The origin of the question is The Junction Transistor in chapter Transistor Characteristics of Electronic Devices & Circuits
Answer» Correct choice is (c) the collector is made physically LARGER than the emitter region Explanation: In most of the TRANSISTORS, the collector is made larger than emitter region. This is DUE to the fact that collector has to DISSIPATE MUCH greater power. The collector and emitter cannot be interchanged.

Discussion

60.	The grown junction type transistors is generally used for_________(a) PNP transistors(b) NPN transistors(c) Both transistors(d) Depends on the material usedThis question was posed to me in examination.The doubt is from Transistor Construction in section Transistor Characteristics of Electronic Devices & Circuits
Answer» The correct choice is (b) NPN transistors For explanation I would say: Grown JUNCTION TYPE transistors are manufactured through growing SINGLE large crystal which is slowly PULLED from the melt in crystal growing furnace. This is generally USED for NPN transistors.

Discussion

61.	For the BJT, β=∞, VBEon=0.7V VCEsat=0.7V. The switch is initially closed. At t=0, it is opened. At which time the BJT leaves the active region?(a) 20ms(b) 50ms(c) 60ms(d) 70msThis question was posed to me in a job interview.I'm obligated to ask this question of Transistor Switching Times topic in section Transistor Characteristics of Electronic Devices & Circuits
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62.	In the operation of an NPN transistor, the electrons cross which region?(a) emitter region(b) the region where there is high depletion(c) the region where there is low depletion(d) P type base regionI got this question in quiz.The doubt is from The Junction Transistor topic in portion Transistor Characteristics of Electronic Devices & Circuits
Answer» Correct answer is (d) P type base region Easy explanation: The electrons in the emitter region are repelled by the negative terminal of the BATTERY towards the emitter junction. The potential BARRIER at the junction is REDUCED due to FORWARD bias and base region is very thin and lightly doped, electrons CROSS the P type base region.

Discussion

63.	Switching speed of P+ junction depends on _________(a) Mobility of minority carriers in P junction(b) Life time of minority carriers in P junction(c) Mobility of majority carriers in N junction(d) Life time of minority carriers in N junctionI have been asked this question during an internship interview.Question is taken from Transistor Switching Times topic in portion Transistor Characteristics of Electronic Devices & Circuits
Answer» RIGHT option is (d) Life time of minority carriers in N junction Explanation: Switching leads to move holes in P region to N region as minority carriers. REMOVAL of this ACCUMULATION determines switching speed. P+ REGARDS to a diode in which the p type is doped EXCESSIVELY.

Discussion

64.	Which of the following is true about grown junction type construction?(a) N type impurity is added to P type impurity(b) Boron helps in the preventionof oxidation(c) The seed is pulled to a large distance for a correct growth(d) Slow pulling leads to the formation of P type crystalThis question was posed to me in semester exam.This is a very interesting question from Transistor Construction in portion Transistor Characteristics of Electronic Devices & Circuits
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Discussion

65.	The switching of power with a PNP transistor is called _________(a) sourcing current(b) sinking current(c) forward sourcing(d) reverse sinkingThis question was addressed to me at a job interview.Question is taken from Transistor Switching Times in chapter Transistor Characteristics of Electronic Devices & Circuits
Answer» The CORRECT option is (a) sourcing current For explanation: Sometimes DC current GAIN of a bipolar transistor is too low to directly SWITCH the load current or VOLTAGE, so multiple switching transistors is used. The load is connected to ground and the transistor switches the power to it.

Discussion

66.	What is the DC characteristic used to prove that the transistor is indeed biased in saturation mode?(a) IC = βIB(b) IC > βIB(c) IC >> βIB(d) IC < βIBThe question was posed to me in unit test.This is a very interesting question from DC Load Lines topic in portion Transistor Characteristics of Electronic Devices & Circuits
Answer» Right answer is (d) IC < βIB The explanation is: When in a transistor is driven into saturation, we use VCE(SAT) as anotherlinear PARAMETER. In, addition when a transistor is biased in saturation MODE, we have IC < βIB. This CHARACTERISTIC used to prove that the transistor is indeed biased in saturation mode.

Discussion

67.	The time taken for a transistor to turn from saturation to cut off is _________(a) inversely proportional to charge carriers(b) directly proportional to charge carriers(c) charging time of the capacitor(d) discharging time of the capacitorI had been asked this question in an internship interview.The above asked question is from Transistor Switching Times topic in division Transistor Characteristics of Electronic Devices & Circuits
Answer» RIGHT option is (b) DIRECTLY PROPORTIONAL to charge carriers Easy explanation: When sufficient charge carriers exist, the transistor GOES into saturation. When the SWITCH is turned off, in order to go into cut off, the charge carriers in the base region need to leave. The longer it takes to leave, the longer it takes for a transistor to turn from saturation to cut off.

Discussion

68.	The base current amplification factor β is given by_________(a) IC/IB(b) IB/IC(c) IE/IB(d) IB/IEThe question was asked by my college director while I was bunking the class.This is a very interesting question from The Common Emitter Configuration topic in section Transistor Characteristics of Electronic Devices & Circuits
Answer» Right answer is (a) IC/IB Explanation: The current AMPLIFICATION FACTOR (β) is given by IC//IB. When no signal is APPLIED, then the ratio of COLLECTOR current to the BASE current is called current amplification factor of a transistor.

Discussion

69.	In a grown junction type construction, the method used form a junction transistor is_________(a) alloy type diffusion(b) mesa type(c) speed variation method(d) fused junction typeI got this question in an international level competition.I'm obligated to ask this question of Transistor Construction topic in chapter Transistor Characteristics of Electronic Devices & Circuits
Answer» Correct answer is (c) SPEED variation method Explanation: The GROWN junction may be formed by suddenly varying the RATE of pulling the seed CRYSTAL from the MELT. This method is based on the fact that proportion in which N and P type impurities crystallise i.e.., enter the grown crystal depends on the rate of pulling.

Discussion

70.	The change in output voltage across the load resistor for a transistor during amplification is_________(a) RL α∆IE(b) RL ∆IE/α(c) RL α^2∆IE(d) RL α^1/2*∆IEI have been asked this question in examination.This question is from The Transistor as an Amplifier topic in division Transistor Characteristics of Electronic Devices & Circuits
Answer» Correct ANSWER is (a) RL α∆IE The best explanation: A SMALL change of voltage ∆Vi between EMITTER and base causes a relatively large emitter CURRENT change ∆IE. We define by the symbol α that fraction of this current change which is collected and PASSES through RL.

Discussion

71.	In a PNP transistor operating in active region, the main stream of current is_________(a) drift of holes(b) drift of electrons(c) diffusion of holes(d) diffusion of electronsI had been asked this question in a national level competition.Asked question is from The Transistor as an Amplifier topic in section Transistor Characteristics of Electronic Devices & Circuits
Answer» The CORRECT answer is (c) diffusion of holes Easiest explanation: The emitter-base junction is forward biased while collector-base junction is REVERSED biased. The transistor now OPERATES in active region. Here, it can be USED for amplification purpose.

Discussion

72.	The transfer of a signal in a transistor is_________(a) low to high resistance(b) high to low resistance(c) collector to base junction(d) emitter to base junctionThe question was posed to me by my school principal while I was bunking the class.I'd like to ask this question from The Junction Transistor topic in portion Transistor Characteristics of Electronic Devices & Circuits
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Discussion

73.	The current gain of the CB transistor is_________(a) less than or equal to unity(b) equal to unity(c) greater than unity(d) remains sameThe question was asked during an interview for a job.This question is from The CB Characteristics topic in section Transistor Characteristics of Electronic Devices & Circuits
Answer» Right option is (a) LESS than or EQUAL to unity To explain: The input current flowing into the emitter TERMINAL must be higher than the base current and collector current to operate the transistor. Therefore the output collector current is less than the input emitter current.

Discussion

74.	A transistor has an IC of 100mA and IB of 0.5mA. What is the value of αdc?(a) 0.565(b) 0.754(c) 1.24(d) 0.995I have been asked this question in exam.My doubt stems from The Transistor as an Amplifier topic in division Transistor Characteristics of Electronic Devices & Circuits
Answer» The CORRECT ANSWER is (d) 0.995 To EXPLAIN: EMITTER CURRENT IE=IC+IB=100+0.5=100.5mA. αdc=IC/IE=100/100.5=0.995.

Discussion

75.	The emitter current IE in a transistor is 3mA. If the leakage current ICBO is 5µA and α=0.98, calculate the collector and base current.(a) 3.64mA and 35µA(b) 2.945mA and 55µA(c) 3.64mA and 33µA(d) 5.89mA and 65µAThe question was asked during an online exam.This intriguing question comes from The Common Base Configuration topic in section Transistor Characteristics of Electronic Devices & Circuits
Answer» The CORRECT OPTION is (B) 2.945mA and 55µA The BEST I can EXPLAIN: IC=αIE + ICBO =0.98*3+0.005=2.945mA. IE=IC+IB . So, IB=3-2.495=0.055mA=55µA.

Discussion

76.	When the collector junction is reverse biased and emitter junction is forward biased, the operating region of the transistor is called_________(a) inverted region(b) active region(c) cut off region(d) cut in regionI had been asked this question in a national level competition.Question is taken from The CB Characteristics in division Transistor Characteristics of Electronic Devices & Circuits
Answer» The correct choice is (b) active region Best EXPLANATION: In the active region, for SMALL values of BASE current, the effect of collector voltage over collector current is small while for large base currents this effect INCREASES. The shape of CHARACTERISTIC here is same as that of CB transistors.

Discussion

77.	The small amount of current which flows even when base current IB=0 is called_________(a) IBEO(b) ICBO(c) ICEO(d) ICThis question was posed to me in my homework.My question is from The CE Characteristics topic in section Transistor Characteristics of Electronic Devices & Circuits
Answer» The correct choice is (C) ICEO To explain I WOULD say: In the cut off region, a small amount of COLLECTOR current flows even when base current IB is zero. This is called ICEO. Since the main current is also zero, the TRANSISTOR is SAID to be cut off.

Discussion

78.	The application of a CC configured transistor is_________(a) voltage multiplier(b) level shifter(c) rectification(d) impedance matchingThis question was addressed to me in exam.I'd like to ask this question from The Common Collector Configuration topic in division Transistor Characteristics of Electronic Devices & Circuits
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Discussion

79.	A common base transistor amplifier has an input resistance of 20Ω and output resistance of 100kΩ. If a signal of 400mV is applied between emitter and base, find the voltage amplification. Assume αac to be one.(a) 20(b) 50(c) 30(d) 25I have been asked this question by my college director while I was bunking the class.I'm obligated to ask this question of The Transistor as an Amplifier topic in section Transistor Characteristics of Electronic Devices & Circuits
Answer» RIGHT ANSWER is (B) 50 Explanation: IE = V/R=400M/20=20mA IC=αIE= 120mA=20mA. VO=ICRL=20m*1k=20V Amplification, A= VO/signal voltage=20V/400m=50.

Discussion

80.	The switching of power with a PNP transistor is called_________(a) sourcing current(b) sinking current(c) forward sourcing(d) reverse sinkingThis question was addressed to me in an online quiz.Question is taken from Transistor as a Switch in portion Transistor Characteristics of Electronic Devices & Circuits
Answer» The correct option is (a) sourcing current Explanation: Sometimes DC current gain of a BIPOLAR transistor is too low to DIRECTLY SWITCH the LOAD current or voltage, so multiple switching transistors is used. The load is connected to ground and the transistor switches the power to it.

Discussion

81.	For the circuit shown, find the quiescent point.(a) (6V, 1mA)(b) (4V, 10mA)(c) (10V, 3mA)(d) (3mA, 10V)I have been asked this question in an interview.The origin of the question is DC Load Lines in division Transistor Characteristics of Electronic Devices & Circuits
Answer» Correct option is (c) (10V, 3mA) The BEST I can explain: We know, VCE=12V (IC)SAT =VCC/RL=12/6K=2mA. IB=10V/0.5M=20µA. IC= βIB=1mA. I VCE=VCC-ICRL=12-1*6=6V. So, quiescent point is (6V, 1mA).

Discussion

82.	In CE configuration, if the voltage drop across 5kΩ resistor connected in the collector circuit is 5V. Find the value of IB when β=50.(a) 0.01mA(b) 0.25mA(c) 0.03mA(d) 0.02mAI have been asked this question in an internship interview.The doubt is from The Common Emitter Configuration in section Transistor Characteristics of Electronic Devices & Circuits
Answer» CORRECT ANSWER is (d) 0.02mA The BEST EXPLANATION: IC=V ACROSS RL/RL=5V/5KΩ=1mA. IB=IC/β=1/50=0.02mA.

Discussion

83.	A germanium transistor with α=0.98 gives a reverse saturation current ICBO=10µA in a CB configuration. When it is used in CE configuration with a base current of 0.22µA, calculate the collector current.(a) 0.9867mA(b) 0.7654mA(c) 0.51078mA(d) 0.23456mAThe question was posed to me in examination.My doubt is from The Common Emitter Configuration topic in portion Transistor Characteristics of Electronic Devices & Circuits
Answer» The CORRECT option is (C) 0.51078mA Easy explanation: GIVEN, ICBO=10µA, α=0.98 and IB =0.22µA. IC=α/ (1-α) IB+ 1/(1-α) ICBO 0.01078+0.5=0.51078mA.

Discussion

84.	A transistor has an IE of 0.9mA and amplification factor of 0.98. What will be the IC?(a) 0.745mA(b) 0.564mA(c) 0.236mA(d) 0.882mAThe question was asked in an interview for internship.My question is from The Common Base Configuration topic in section Transistor Characteristics of Electronic Devices & Circuits
Answer» RIGHT ANSWER is (d) 0.882mA For explanation I would say: GIVEN, IE = 0.9mA, α=0.98 We know, α= IC/IE So, IC=0.98*0.9=0.882mA.

Discussion

85.	Which gas is used to fill the chamber in the grown junction type transistor construction?(a) helium(b) boron(c) nitrogen(d) oxygenI have been asked this question in my homework.I need to ask this question from Transistor Construction in section Transistor Characteristics of Electronic Devices & Circuits
Answer» RIGHT choice is (c) nitrogen For explanation I would say: In the process of TRANSISTOR CONSTRUCTION, a crucible is placed in the chamber. This chamber consists of hydrogen or nitrogen. These gases HELP in the prevention of oxidation. It also contains purified GE or Si at a temperature few degrees above its melting point.

Discussion

86.	In saturation region, the depletion layer_________(a) increases linearly with carrier concentration(b) decreases linearly with carrier concentration(c) increases by increasing the emitter current(d) decreases by decreasing the emitter voltage dropI have been asked this question in unit test.My doubt is from Transistor as a Switch topic in chapter Transistor Characteristics of Electronic Devices & Circuits
Answer» Right option is (d) decreases by decreasing the EMITTER voltage drop Best explanation: Here, the transistor will be biased so that maximum AMOUNT of base current is applied, resulting in maximum collector current resulting in MINIMUM emitter voltage drop which results in depletion LAYER as small as possible and maximum current flows through the transistor.

Discussion

87.	The relation between α and β is _________(a) β=α/(1-α)(b) α= β/(1+β)(c) β=α/(1+α)(d) α= β/(1- β)I have been asked this question in an international level competition.This intriguing question comes from The Common Base Configuration in division Transistor Characteristics of Electronic Devices & Circuits
Answer» RIGHT choice is (b) α= β/(1+β) To elaborate: β is an ac base AMPLIFICATION factor. α is CALLED as current amplification factor. The relation of IC and IB change as IC= βIB+ (1+ β)ICBO.

Discussion

88.	In which region a transistor acts as an open switch?(a) cut off region(b) inverted region(c) active region(d) saturated regionI had been asked this question during an interview for a job.Query is from Transistor as a Switch in division Transistor Characteristics of Electronic Devices & Circuits
Answer» RIGHT option is (a) cut off region The best EXPLANATION: In this mode, both the junctions are reverse biased. The transistor has practically zero current because the emitter does not emit charge CARRIERS to the base. There is negligibility current due to minority carriers. In this mode the transistor acts as an OPEN switch.

Discussion

89.	When is the transistor said to be saturated?(a) when VCE is very low(b) when VCE is very high(c) when VBE is very low(d) when VBE is very highI had been asked this question in homework.This intriguing question originated from The Common Collector Configuration in section Transistor Characteristics of Electronic Devices & Circuits
Answer» Right answer is (a) when VCE is very low Explanation: When VCE is very low, the TRANSISTOR said to be saturated and it operates in saturated region of characteristic. The CHANGE in base CURRENT IB does not PRODUCE a corresponding change in the collector voltage IC.

Discussion

90.	What is the other representation of the given PNP transistor connected in common emitter configuration?I got this question during an interview for a job.My doubt stems from DC Load Lines topic in section Transistor Characteristics of Electronic Devices & Circuits
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Discussion

91.	In an NPN transistor, the arrow is pointed towards_________(a) the collector(b) the base(c) depends on the configuration(d) the emitterI got this question during an online interview.This question is from The Junction Transistor in chapter Transistor Characteristics of Electronic Devices & Circuits
Answer» Right answer is (d) the emitter For explanation I would SAY: As regards to the symbols, the arrow head is always at the emitter. The DIRECTION indicates the CONVENTIONAL direction of current flow. In CASE of PNP transistor, it is from BASE to emitter.

Discussion

92.	The advantages over the vacuum triode for a junction transistor is_________(a) high power consumption(b) high efficiency(c) large size(d) less dopingI have been asked this question during an interview.This is a very interesting question from The Junction Transistor in division Transistor Characteristics of Electronic Devices & Circuits
Answer» RIGHT option is (B) high efficiency Best explanation: A junction transistor is an analogous to a vacuum triode. The main difference between them is that a transistor is a current DEVICE while a vacuum triode is a voltagedevice. The advantages of a transistor over a vacuum triode are long life, high efficiency, light weight, smaller in SIZE, less power consumption.

Discussion

Explore topic-wise InterviewSolutions in .

The DC equivalent circuit for an NPN common base circuit is.I got this question by my college professor while I was bunking the class.My question comes from DC Load Lines in chapter Transistor Characteristics of Electronic Devices & Circuits

The current amplification factor ϒdc is given by_________(a) IE/IB(b) IB/IE(c) IC/IE(d) IE/ICI got this question in quiz.Query is from The Common Collector Configuration topic in portion Transistor Characteristics of Electronic Devices & Circuits

Which of the following corresponds to the output circuit of a CB transistor?(a) VBE(b) IB(c) VCB(d) VCEThis question was addressed to me in an international level competition.The doubt is from The CB Characteristics in portion Transistor Characteristics of Electronic Devices & Circuits

A transistor has an IC of 100mA and IB of 0.5mA. What is the value of αdc?(a) 0.565(b) 0.754(c) 1.24(d) 0.995I have been asked this question in exam.My doubt stems from The Transistor as an Amplifier topic in division Transistor Characteristics of Electronic Devices & Circuits

The small amount of current which flows even when base current IB=0 is called_________(a) IBEO(b) ICBO(c) ICEO(d) ICThis question was posed to me in my homework.My question is from The CE Characteristics topic in section Transistor Characteristics of Electronic Devices & Circuits

For the circuit shown, find the quiescent point.(a) (6V, 1mA)(b) (4V, 10mA)(c) (10V, 3mA)(d) (3mA, 10V)I have been asked this question in an interview.The origin of the question is DC Load Lines in division Transistor Characteristics of Electronic Devices & Circuits

In which region a transistor acts as an open switch?(a) cut off region(b) inverted region(c) active region(d) saturated regionI had been asked this question during an interview for a job.Query is from Transistor as a Switch in division Transistor Characteristics of Electronic Devices & Circuits

What is the other representation of the given PNP transistor connected in common emitter configuration?I got this question during an interview for a job.My doubt stems from DC Load Lines topic in section Transistor Characteristics of Electronic Devices & Circuits

In an NPN transistor, the arrow is pointed towards_________(a) the collector(b) the base(c) depends on the configuration(d) the emitterI got this question during an online interview.This question is from The Junction Transistor in chapter Transistor Characteristics of Electronic Devices & Circuits