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Unit 2: Bipolar Junction Transistor (BJT) - Practice Quiz

ECE226 — Analog Electronic Devices And Circuits 60 Questions
0 Correct 0 Wrong 60 Left
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1 A BJT consists of how many terminals?

PNP and NPN transistors Easy
A. Two
B. Three
C. Five
D. Four

2 In an NPN transistor, the base region is made of which type of semiconductor material?

PNP and NPN transistors Easy
A. Intrinsic
B. Metal
C. N-type
D. P-type

3 In a PNP transistor, the majority charge carriers responsible for current flow are:

PNP and NPN transistors Easy
A. Holes
B. Photons
C. Electrons
D. Ions

4 For normal (active region) operation of an NPN transistor, the base-emitter junction should be:

PNP and NPN transistors Easy
A. Left open
B. Forward biased
C. Short circuited
D. Reverse biased

5 Which equation correctly relates the three terminal currents of a BJT?

Current components in BJT Easy
A.
B.
C.
D.

6 The current gain in the common-base configuration is defined as the ratio of:

Current components in BJT Easy
A. to
B. to
C. to
D. to

7 The typical value of the common-base current gain is:

Current components in BJT Easy
A. Greater than 1
B. Exactly 0
C. Slightly less than 1
D. Around 100

8 The relationship between and of a BJT is given by:

Current components in BJT Easy
A.
B.
C.
D.

9 The input characteristic of a BJT in CE configuration is a plot of:

BJT static characteristics (Input and Output) Easy
A. vs
B. vs
C. vs
D. vs

10 The output characteristic of a BJT in CE configuration is a plot of:

BJT static characteristics (Input and Output) Easy
A. vs
B. vs
C. vs
D. vs

11 The Early effect in a BJT refers to the variation of:

Early effect Easy
A. Base width with collector voltage
B. Emitter width with base current
C. Base doping with temperature
D. Collector area with voltage

12 When extended, the output characteristic lines of a BJT meet at a point on the voltage axis known as the:

Early effect Easy
A. Breakdown voltage
B. Threshold voltage
C. Pinch-off voltage
D. Early voltage

13 Which BJT configuration provides the highest voltage and current gain simultaneously?

CB, CC, CE configurations Easy
A. Common Gate
B. Common Collector (CC)
C. Common Base (CB)
D. Common Emitter (CE)

14 The Common Collector (CC) configuration is also commonly known as a:

CB, CC, CE configurations Easy
A. Base follower
B. Emitter follower
C. Current mirror
D. Collector follower

15 Which configuration is best suited for use as a buffer due to its high input impedance and low output impedance?

CB, CC, CE configurations Easy
A. Common Source
B. Common Base (CB)
C. Common Emitter (CE)
D. Common Collector (CC)

16 In the cut-off region of a BJT, both junctions are:

Cut off, active, and saturation regions Easy
A. Forward biased
B. Reverse biased
C. One forward, one reverse
D. Zero biased

17 In the saturation region, both junctions of a BJT are:

Cut off, active, and saturation regions Easy
A. One forward, one reverse
B. Reverse biased
C. Zero biased
D. Forward biased

18 For a BJT to be used as an amplifier, it should be operated in the:

Cut off, active, and saturation regions Easy
A. Saturation region
B. Active region
C. Breakdown region
D. Cut-off region

19 In a two-port network representation, how many parameters describe the network?

CE configuration as two port network Easy
A. Three
B. Two
C. Four
D. Six

20 The h-parameter in the CE configuration represents the:

h parameters Easy
A. Reverse voltage gain
B. Output admittance
C. Input impedance
D. Forward current gain

21 In an NPN transistor operating in the active region, the emitter current is and the base current is . What is the value of the common-base current gain ?

Current components in BJT Medium
A.
B.
C.
D.

22 A BJT has a common-emitter current gain . What is the corresponding common-base current gain ?

Current components in BJT Medium
A.
B.
C.
D.

23 For a PNP transistor to operate in the active region, how must the junctions be biased?

PNP and NPN transistors Medium
A. Both junctions reverse biased
B. Emitter-base forward biased, collector-base reverse biased
C. Both junctions forward biased
D. Emitter-base reverse biased, collector-base forward biased

24 A silicon NPN transistor has and measured during operation. In which region is the transistor operating?

Cut off, active, and saturation regions Medium
A. Active
B. Saturation
C. Cut off
D. Breakdown

25 The Early effect in a BJT is primarily caused by which physical phenomenon?

Early effect Medium
A. Thermal runaway due to junction heating
B. Increase in emitter injection efficiency at high currents
C. Widening of the collector-base depletion region reducing effective base width
D. Recombination of carriers in the emitter region

26 A transistor has an Early voltage and a collector current at . What is the approximate output resistance ?

Early effect Medium
A.
B.
C.
D.

27 Which BJT configuration provides high voltage gain and high current gain but a phase inversion of between input and output?

CB, CC, CE configurations Medium
A. Emitter Follower
B. Common Base (CB)
C. Common Collector (CC)
D. Common Emitter (CE)

28 The Common Collector (CC) configuration is most suitable for which application?

CB, CC, CE configurations Medium
A. Signal phase inversion
B. High frequency oscillation
C. Impedance matching / buffering
D. High voltage amplification

29 In the h-parameter model, the parameter represents which quantity in the CE configuration?

h parameters Medium
A. Input impedance with output short-circuited
B. Forward current gain with output short
C. Reverse voltage gain with input open
D. Output admittance with input open-circuited

30 The h-parameter in the common-emitter configuration corresponds to which of the following?

h parameters Medium
A. Forward current gain with output short-circuited
B. Input resistance with output open
C. Output conductance with input shorted
D. Reverse voltage transfer ratio

31 In the h-parameter equivalent circuit of a BJT, the term appears as which element in the input loop?

h parameter equivalent circuit Medium
A. A current source dependent on the input current
B. A conductance across the output
C. A resistance in series with the input
D. A voltage source dependent on the output voltage

32 In the CE output characteristics of a BJT, the nearly flat portion of the curves (constant for increasing ) corresponds to which region?

BJT static characteristics (Input and Output) Medium
A. Breakdown region
B. Cut off region
C. Saturation region
D. Active region

33 The CE input characteristic (plot of vs ) of a BJT most closely resembles which of the following?

BJT static characteristics (Input and Output) Medium
A. A forward-biased diode characteristic
B. A reverse-biased diode characteristic
C. A straight line through the origin
D. A parabolic curve

34 A CE amplifier has and a collector resistor . What is the maximum collector current (the intercept of the DC load line on the axis)?

Biasing and load line analysis Medium
A.
B.
C.
D.

35 For a stable Q-point and good thermal stability, which biasing method is generally preferred?

Biasing and load line analysis Medium
A. Voltage divider bias
B. Fixed base bias
C. Base bias with a single resistor
D. Collector-to-base bias without feedback

36 In a fixed-bias CE circuit, , , and . What is the base current ?

Biasing and load line analysis Medium
A.
B.
C.
D.

37 When the CE configuration is treated as a two-port network using h-parameters, which two are the independent (input) variables chosen?

CE configuration as two port network Medium
A. Input voltage and output voltage
B. Input current and output current
C. Input voltage and output current
D. Input current and output voltage

38 On a BJT datasheet, the parameter specifies which of the following?

understanding datasheets of BJTs Medium
A. Maximum collector-emitter voltage with base open
B. Collector-emitter saturation voltage
C. Maximum collector current at saturation
D. Base-emitter turn-on voltage

39 A BJT datasheet lists . If the device operates at , what is the maximum allowable collector current before exceeding power dissipation?

understanding datasheets of BJTs Medium
A.
B.
C.
D.

40 A BJT with has . The circuit can supply a maximum before saturation. Is the transistor in active or saturation, and why?

Cut off, active, and saturation regions Medium
A. Saturation, since
B. Active, since exactly
C. Active, since flows freely
D. Cut off, since is too small

41 In an NPN transistor operating in the active region, the emitter current is , the base transport factor , and the emitter injection efficiency . If the reverse saturation collector-base current , what is the collector current ?

Current components in BJT Hard
A.
B.
C.
D.

42 A transistor in CE configuration has , , , and . For a load resistance , what is the voltage gain ?

h parameters Hard
A.
B.
C.
D.

43 A BJT has an Early voltage and collector current at . What is the output resistance of the transistor?

Early effect Hard
A.
B.
C.
D.

44 In a fixed-bias CE circuit, , , , , and . What is the collector-emitter voltage at the Q-point?

Biasing and load line analysis Hard
A.
B.
C.
D.

45 A BJT with has , , , , and . Is the transistor in saturation, and what is the saturation collector current?

Cut off, active, and saturation regions Hard
A. Active;
B. Saturated;
C. Saturated;
D. Cut off;

46 For a transistor with , if the base current increases by in the CE configuration, by how much does the collector current change (assuming ideal behavior)?

CB, CC, CE configurations Hard
A.
B.
C.
D.

47 In the CE output characteristics, the slope of the curves in the active region is nonzero primarily because of which effect, and what does the reciprocal of this slope represent?

BJT static characteristics (Input and Output) Hard
A. Punch-through; reverse gain
B. Base-width narrowing; transconductance
C. Early effect; output resistance
D. Avalanche breakdown; input resistance

48 In the h-parameter model, the parameter (reverse voltage gain) physically models which phenomenon in the CE amplifier?

h parameter equivalent circuit Hard
A. Feedback of output voltage to the input due to base-width modulation
B. Input resistance seen looking into the base terminal
C. Forward current amplification from base to collector
D. Output conductance due to leakage current

49 For the CE two-port hybrid model, which set of variables are treated as independent inputs?

CE configuration as two port network Hard
A. Input current and output current
B. Input voltage and output current
C. Input current and output voltage
D. Input voltage and output voltage

50 A voltage-divider bias circuit has , , , , , . Using the exact analysis, what is ? (Include base current.)

Biasing and load line analysis Hard
A.
B.
C.
D.

51 If a transistor's base doping is increased while keeping the base width constant, what happens to the Early voltage and why?

Early effect Hard
A. increases because higher base doping reduces depletion-region widening into the base
B. stays constant because it depends only on collector doping
C. decreases because higher doping lowers the collector current
D. decreases because higher doping increases base recombination

52 For a PNP transistor operating correctly in the active region, which biasing condition on the terminal voltages is required?

PNP and NPN transistors Hard
A.
B.
C. and
D.

53 In an NPN transistor, the total emitter current consists of electron injection into the base () and hole injection into the emitter (). If and , what is the emitter injection efficiency ?

Current components in BJT Hard
A.
B.
C.
D.

54 A BJT datasheet lists at with a derating factor of . What is the maximum allowable power dissipation at an ambient temperature of ?

understanding datasheets of BJTs Hard
A.
B.
C.
D.

55 Which BJT configuration provides voltage gain greater than one, current gain greater than one, and a phase inversion, making it suitable as a general-purpose amplifier?

CB, CC, CE configurations Hard
A. Common Collector (CC)
B. Common Base (CB)
C. Common Emitter (CE)
D. Emitter Follower

56 A CE amplifier has , , and a Q-point at . What is the maximum symmetrical peak-to-peak output voltage swing before clipping (ignoring )?

Biasing and load line analysis Hard
A.
B.
C.
D.

57 Given CE parameters and , and a load , what is the current gain of the CE amplifier?

h parameters Hard
A.
B.
C.
D.

58 In the saturation region of a BJT, which statement about the junction biasing and collector current is correct?

Cut off, active, and saturation regions Hard
A. Both junctions are reverse biased and
B. Both junctions are forward biased and
C. Only the collector junction is forward biased and
D. Both junctions are forward biased and

59 In the CB input characteristics ( vs ), increasing (magnitude of reverse bias) causes the curve to shift such that for the same , increases. This is a manifestation of which effect?

BJT static characteristics (Input and Output) Hard
A. Early effect (base-width modulation)
B. Thermal runaway
C. Emitter crowding
D. Avalanche multiplication

60 A datasheet specifies ranging from 100 to 300 for the same transistor type. What is the most important design implication of this wide spread?

understanding datasheets of BJTs Hard
A. Only the maximum value should be used in all calculations
B. Bias circuits must be designed to make the Q-point relatively independent of
C. The transistor cannot be used for amplification
D. The collector current will always be exactly the mean value
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