BJT Question & Answers October 25, 2021 By WatElectronics This article lists 100 BJT MCQs for engineering students. All the BJT Questions & Answers given below include a hint and a link wherever possible to the relevant topic. This is helpful for users who are preparing for their exams, interviews, or professionals who would like to brush up their fundamentals on BJTs. BJT stands for Bipolar Junction Transistor and it is a semiconductor device, invented by William Shockley, John Bardeen, and Brattain in the year 1948. The purpose of BJT is to amplify the current in it. It comprises 3 terminals namely, base, emitter, and collector, and are available in 2 configurations like NPN and PNP configuration forming junction regions during operation. These transistors are used in many applications such as switches, amplifiers, clippers, and more. They provide benefits in terms of enhanced frequency of operation, high voltage gain, enhanced bandwidth, and low forward drop in voltage. But they limit in terms of low stability, low frequency of switching, and noise. 1). Which of the following scientist invented BJT? William Shockley Brattain John Bardeen All the above None Hint 2). Which of the following are the charge carriers available in BJT? Holes Electrons Neutrons Both a and b None Hint 3). Which of the following are the semiconductors class used in BJT? P-type N-type PN-type Both a and b None Hint Read more about semiconductors. 4). Identify the main function of a BJT? Acts as amplifier Acts as a switch Acts as a rectifier Both a and b None Hint 5). Identify the applications of BJT? Clippers Digital switch Temperature sensors All the above None Hint Read more about sensors. 6). Identify the availability configuration of BJT? PNP NPN NPNP Both a and b None Hint 7). Which of the following are majority charge carriers in NPN BJT? Holes Electrons Neutrons Protons None Hint 8). Which of the following are minority charge carriers in NPN BJT? Holes Electrons Neutrons Both b and c None Hint 9). Which of the following are majority charge carriers in PNP BJT? Holes Electrons Neutrons Both b and c None Hint 10). Which of the following are minority charge carriers in PNP BJT? Holes Electrons Neutrons Protons None Hint 11). A hole is represented with ___ polarity? + - * / None Hint 12). A electron is represented with ___ polarity? + - / * None Hint 13). How many terminals do a BJT have? 1 2 3 4 None Hint 14). A BJT is a ___ electronic component? Resistor Transistor Capacitor Both a and c None Hint 15). In which of the following terminals do current flow inside BJT? Base Collector Emitter Both b and c None Hint 16). Which of the following BJT terminal controls the current flow? Base Collector Emitter Drain None Hint 17). In NPN BJT transistor which of the following terminal defines P-type? Base Collector Emitter Drain None Hint 18). In NPN BJT transistor which of the following terminal defines N-type? Base Collector Emitter Both b and c None Hint 19). In PNP BJT transistor which of the following terminal defines N-type? Base Collector Emitter Drain None Hint 20). In PNP BJT transistor which of the following terminal defines P-type? Base Collector Emitter Both b and c None Hint 21). Identify the junction name when PN junction in BJT is shorts emitter and base terminals? BE junction EB junction BC junction EC junction None Hint 22). Identify the junction name when PN junction in BJT is shorts collector and base terminals? BE junction EB junction BC junction EC junction None Hint Read more about PN junction. 23). Which of the following terminals of BJT are slightly doped? Base Collector Emitter Both b and c None Hint 24). Which of the following terminals of BJT are heavily doped? Base Collector Emitter Both b and c None Hint 25). Which of the following terminals of BJT is extremely thin? Base Collector Emitter Both b and c None Hint BJT Important Questions for Interviews 26). Which of the following terminals of BJT is thick? Base Collector Emitter Both b and c None Hint 27). Which of the following represents arrow in BJT symbol? Flow of current Flow of resistance Direction of current Both a and c None Hint 28). Which of the following junction in BJT is forward biased? Base Collector Emitter Both a and c None Hint 29). Which of the following terminal in BJT is always maintained in reverse biased state? Base Emitter Collector Drain None Hint 30). Which of the following terminal of BJT emits carriers to other terminals? Base Emitter Collector Drain None Hint 31). Which of the following terminal of BJT collects carriers from other terminals? Base Emitter Collector Drain None Hint 32). Which of the following terminal of BJT eliminates the requirement of flow of charge carriers from collector to base? Base Emitter Collector Drain None Hint 33). A BJT operates in __ number of regions? 1 2 3 4 None Hint 34). In which of the following region do BJT operates in forward bias? Active Cut-off Saturation Both a and c None Hint 35). In which of the following region do BJT operates in reverse bias? Active Cut-off Saturation Both a and c None Hint 36). Which of the following BJT region does amplification? Active Cut-off Saturation Both a and c None Hint 37). Which of the following is the formula for BJT active region? Ic = B * Ib Ic = B / ib Ic = B + ib Ic = B - ib None Hint 38). Which of the following region in BJT is an linear region? Active Cut-off Saturation Both a and c None Hint 39). Which of the following region in BJT is an non-linear region? Active Cut-off Saturation Both b and c None Hint 40). Which of the following is the mid region in BJT characteristics? Active Cut-off Saturation Both b and c None Hint 41). In which of the following BJT region do BJT just begins to operate? Active Cut-off Saturation Both b and c None Hint 42). Which of the following BJT region perform switching? Active Cut-off Saturation Both b and c None Hint 43). Identify the correct formula of BJT saturation region? Ic = Isat Ic = Isat/Iactive Ic = 0 Ic = 1 None Hint 44). Which of the following is the highest value of current ? Isat Icutoff Iactive All the above None Hint 45). In which of the following BJT region acts like a short circuit? Active Cut-off Saturation Both b and c None Hint 46). In which of the following region of BJT the transistors are reverse biased? Active Cut-off Saturation Both b and c None Hint 47). Identify the formula for cutoff region? Ic=0 Ic=Icutoff Ic=infinity All the above None Hint 48). Which of the following BJT region acts like a open circuit? Active Cut-off Saturation Both b and c None Hint 49). What is the cutoff off voltage value of BJT? =0.7 <0.7 >0.7 0.9 None Hint 50). BJT comprises of __ number of transistors? 2 3 4 1 None Hint Read more about Transistor. BJT Questions & Answers for Exams 51). A junction type transistor is classified into ___ types? 2 3 4 5 None Hint 52). How many electrodes do a junction type BJT transistor has? 2 3 4 5 None Hint 53). In PNP transistor ___ terminal is given positive polarity? Base Emitter Collector Drain None Hint 54). In PNP transistor ___ terminal is given negative polarity? Base Emitter Collector Drain None Hint 55). In NPN transistor __ terminal is given negative polarity? Base Emitter Collector Drain None Hint 56). In NPN transistor __ terminal is given positive polarity? Base Emitter Collector Drain None Hint 57). A PNP BJT is said to be in ON when voltage of base with respect to emitter is ___? Equal Zero Increased Decreased None Hint 58). What is the equation of current gain in BJT CB configuration? Ic/ie Ie/Ic Ib/ic All the above None Hint 59). What is the equation of resistance gain of BJT common base configuration? RL/Rin Rin/RL RL*Rin RL-Rin None Hint 60). What is the equation of voltage gain of BJT common base configuration? Av= RIN * Ic [RL/IE] Av= RIN [RL/IE] Av= RIN * Ic [RL + IE] Av= RIN * Ic [RL - IE] None Hint 61). Which of the following terminal is grounded in common base configuration of BJT? Base Emitter Collector Drain None Hint 62). Which of the following terminal is grounded in common collector configuration of BJT? Base Emitter Collector Drain None Hint 63). Which of the following terminal is grounded in common emitter configuration of BJT? Base Emitter Collector Drain None Hint 64). What is gain value of common base BJT? = 1 <1 >1 0 None Hint 65). What is the value of phase in of common base BJT? 180 degrees 90 degrees Equal Zero None Hint 66). A common base BJT has _______ voltage gain? High Low Zero 1 None Hint 67). A common base BJT has __ value of frequency response? High Low Zero None Hint 68). A common base is suitable for __ phase type amplifier? 1 2 3 Multi None Hint 69). Which of the following are the application of common base type BJT? RF amplifier Microphone Pre amplifier All the above None Hint Read more about Amplifiers. 70). To which of the following terminal in common base configuration of BJT input supply is given? Base Collector Emitter Both a and c None Hint 71). To which of the following terminal in common base configuration of BJT output value is obtained? Base Collector Emitter Both a and c None Hint 72). At which terminal in common base configuration of BJT the signal is low? Emitter Collector Base All the above None Hint 73). To which of the following terminal in common emitter configuration of BJT input supply is given? Base Collector Emitter Both a and c None Hint 74). To which of the following terminal in common emitter configuration of BJT output is obtained? Base Collector Emitter Both a and c None Hint 75). Which of the following BJT configuration has maximum power gain? CB CE CC Both b and c None Hint BJT MCQs for Quiz 76). Identify the equation of common emitter current of BJT? Ie=Ic+Ib Ie=Ic-Ib Ie=Ic/Ib Ie=Ic*Ib None Hint 77). The value of input impedance of common base configuration of BJT is _______? High Low Medium Zero None Hint 78). The value of input impedance of common emitter configuration of BJT is _______? High Low Medium Zero None Hint 79). The value of input impedance of common collector configuration of BJT is _______? High Low Medium Zero None Hint 80). The value of output impedance of common collector configuration of BJT is _______? High Low Medium Zero None Hint 81). The value of output impedance of common emitter configuration of BJT is _______? High Low Medium Zero None Hint 82). The value of output impedance of common base configuration of BJT is _______? High Low Medium Zero None Hint 83). The value of phase angle of CE is _______? 0 180 90 45 None Hint 84). The power gain of common base configuration of BJT is ______? High Low Medium Zero None Hint 85). The power gain of common emitter configuration of BJT is ______? High Low Medium Zero None Hint 86). The power gain of common collector configuration of BJT is ______? High Low Medium Zero None Hint 87). The value of current gain of common base BJT is ___? High Low Medium Zero None Hint 88. The value of current gain of common emitter BJT is ___? High Low Medium Zero None Hint 89). The value of current gain of common collector BJT is ___? High Low Medium Zero None Hint 90). Which of the following are the advantages provided by BJT? Digital switch High operation frequency High capability of driving All the above None Hint Read more about the switch. 91). The value of emitter current of npn BJT is _________? + - 0 Both a and b None Hint 92). The value of base current of npn BJT is _________? + - Zero Both a and b None Hint 93). The value of collector current of npn BJT is _________? + - Zero Both a and b None Hint 94). The value of emitter base voltage of npn BJT is ______? + - Zero Both a and b None Hint Read more about NPN. 95). The value of collector base voltage of npn BJT is ______? + - Zero Both a and b None Hint 96). The value of collector emitter voltage of npn BJT is ______? + - Zero Both a and b None Hint 97). The value of emitter current of pnp BJT is _____? + - 0 Both a and b None Hint 98). The value of base current of pnp BJT is _____? + - 0 None Hint Read more about PNP. 99). The value of collector current of pnp BJT is _____? + - 0 Both a and b None Hint 100). The value of emitter base voltage of pnp BJT is _____? + - 0 Both a and b None Hint Time's up
