Get all the Bipolar Junction Transistors (BJT) MCQs which have already been asked in previous Engineering service Examinations (ESE) papers or this may come in upcoming exams also. So we have arranged almost all previous papers’ MCQs with answers and explanations given here.
Bipolar Junction Transistors (BJT) MCQs
Que.1 In a junction transistor, the collector cutoff current ICBO reduces considerably by doping the,
- (a) emitter with a high level of impurity
- (b) emitter with a low level of impurity
- (c) collector with a high level of impurity
- (d) collector with a low level of impurity
Que.2 The reverse bias breakdown of high-speed silicon transistors is due to,
- (a) Avalanche breakdown mechanism at both the junction
- (b) Zener breakdown mechanism at both the junctions
- (c) Zener breakdown mechanism at base-collector the junctions
- (d) Zener breakdown mechanism at the base-emitter junction and avalanche breakdown the mechanism in the C-B junction
Que.3 A transistor’s current gain of 0.99 in the CB mode. its current gain in the CC mode is,
- (a) 100
- (b) 99
- (c) 1.01
- (d) 0.99
Que.4 A bipolar junction transistor has a common base forward short circuit current gain of 0.99. Its common emitter forward short circuit current gain will be
- (a) 50
- (b) 99
- (c) 100
- (d) 200
Que.5 How can the channel width in a junction field effect transistor be controlled?
- (a) By two back biased p-n junction
- (b) by the length of the source
- (c) By the length of the drain
- (d) by the lengths of both the source and the drain
Que.6 Which one of the following statements is correct? The set of transistor characteristics that enables \alpha to be directly determined from the slope is
- (a) the common emitter output characteristics
- (b) the common emitter transfer characteristics
- (c) the common base input characteristics
- (d) the common base transfer characteristics
Que.7 The width of the base in a GaAs transistor and in a Si transistor (both n-p-n-type) are equal. GaAs transistor works at a higher frequency. Which one of the following is the correct statement?
- (a) The band gap of GaAs is higher than that of Si.
- (b) The base transit time is lower in GaAs
- (c) The negative differential mobility in GaAs favors operation at a very high frequency.
- (d) Si transistor works at a higher frequency compared to GaAs transistor.
Que.8 Which of the following statements is not correct?
- (a) Reverse saturation current in a BJT approximately doubles for every 10oC rise in temperature.
- (b) The reverse resistance of a junction diode increases with an increase in temperature.
- (c) Reverse saturation current of a silicon diode is much smaller than that of a germanium diode.
- (d) The cut-in voltage of silicon diode is large than that of germanium.
Que.9 For an NPN bipolar transistor, what is the mainstream of current in the base region?
- (a) Drift of holes
- (b) Diffusion of holes
- (c) Drift of electrons
- (d) Diffusion of electrons
Que.10 What is the most noticeable effect of a small increase in temperature in the common emitter connected BJT?
- (a) Increase in ICBO
- (b) Increase in output resistance
- (c) Decrease in forward current gain
- (d) Increase in forward current gain
Que.11 In a junction transistor, recombination of electrons and holes occurs in
- (a) Base region only
- (b) Emitter region only
- (c) Collector region only
- (d) All the 3 regions
Que.12 In a bipolar junction transistor an increase in the magnitude of collector voltage increases the space charge width at the output junction diode. This causes the effective base width of decreases. This effect is known as
- (a) Hall effect
- (b) Early effect
- (c) Miller effect
- (d) Zener effect
Que.13 When a transistor is saturated,
- (a) the emitter potential is more than the base-collector potential.
- (b) the collector potential is more than the base-emitter potential
- (c)the base potential is more than the emitter-collector potential
- (d) the base, emitter, and collector are almost at the same potential
Que.14 if the \alpha value of a transistor changes 0.5% from its normal value of 0.9, the percentage change in \beta will be
- (a) 0%
- (b) 2.5%
- (c) 5%
- (d) 7.5%
Que.15 The early effect in bipolar junction transistor is caused by
- (a) fast turn-on
- (b) fast turn-off
- (c) large emitter to base forward bias
- (d) large collector to base reverse bias
Que.16 A BJT operates as a switch
- (a) in the active region of transfer characteristics
- (b) with no signal condition
- (c) under small signal conditions
- (d) under large signal conditions
Que.17 n-p-n transistors are preferred over p-n-p transistors because they have
- (a) high mobility of holes
- (b) high mobility of electrons
- (c) low mobility of holes
- (d) higher mobility of electrons thane the mobility of holes in p-n-p transistors
Que.18 The leakage current in an NPN transistor is due to the flow of
- (a) Holes from base to emitter
- (b) Electrons from collector to base
- (c) Holes from colletor to base
- (d) Minority carriers from emitter to collector
Que.19 In Early effect
- (a) Increase in the magnitude of collector voltage increases space charge width at the input junction of a BJT
- (b) Increase in the magnitude of Emitter base voltage increases space charge with of output junction of a BJT
- (c) Increase in the magnitude of collector voltage increases the space charge width of the output junction of a BJT
- (d) Decrease in the magnitude of Emitter base voltage increases space charge width of output junction of BJT