1.4 BJT MCQs v2

License Preparation NepalNEC ELECTRONICS

Full marks: 61 · Questions: 61

01BJT Basics

A bipolar junction transistor (BJT) has:

one pn junction

two pn junctions

three pn junctions

four pn junctions

02BJT Basics

The number of depletion layers in a bipolar junction transistor is:

four

three

one

two

03BJT Basics

The base region of a transistor is:

heavily doped

moderately doped

lightly doped

none of the above

04BJT Basics

The element that has the largest physical size in a transistor is:

collector

base

emitter

collector-base-junction

05BJT Basics

In a PNP transistor, the primary current carriers across the junctions are:

acceptor ions

donor ions

free electrons

holes

06BJT Basics

The collector region of a transistor is:

heavily doped

moderately doped

lightly doped

none of the above

07BJT Basics

A bipolar junction transistor is fundamentally a:

current operated device

voltage operated device

both voltage and current operated

none of the above

08BJT Basics

In an NPN transistor, minority charge carriers are:

free electrons

holes

donor ions

acceptor ions

09BJT Basics

The emitter region of a transistor is:

lightly doped

heavily doped

moderately doped

none of the above

10BJT Basics

In a typical transistor, the base current is approximately what percentage of the emitter current?

25%

20%

35%

11BJT Basics

At the forward-biased base-emitter junction of an active transistor, one finds:

a reverse bias

a wide depletion layer

low resistance

none of the above

12BJT Basics

The input impedance of a common-emitter configured transistor is generally:

high

low

very high

almost zero

13BJT Basics

The output impedance of a common-emitter configured transistor is generally:

high

zero

low

very low

14BJT Basics

In a transistor, the signal is transferred from a:

high resistance to low resistance circuit

low resistance to high resistance circuit

high resistance to high resistance circuit

low resistance to low resistance circuit

15BJT Basics

The arrow in the schematic symbol of a transistor indicates the direction of:

electron current in the emitter

electron current in the collector

hole current in the emitter

donor ion current

16BJT Basics

Most of the majority carriers injected from the emitter:

recombine in the base

recombine in the emitter

pass through the base region to the collector

none of the above

17BJT Basics

In an NPN transistor, the base current IB is primarily composed of:

electron current

hole current

donor ion current

acceptor ion current

18BJT Basics

Which relationship among terminal currents is always valid in a transistor?

IC = IE + IB

IB = IC + IE

IE = IC - IB

IE = IC + IB

19BJT Basics

A heat sink is generally attached to a power transistor to:

increase the forward current

decrease the forward current

compensate for excessive doping

prevent excessive temperature rise

20BJT Basics

The most commonly used semiconductor material in the manufacture of transistors is:

germanium

silicon

carbon

none of the above

21BJT Configuration

The common-base current amplification factor α of a transistor is always:

more than 1

less than 1

equal to 1

none of the above

22BJT Configuration

In terms of α, emitter current IE, and reverse saturation current ICBO, collector current is given by IC = αIE + :

ICEO

ICBO

βIB

23BJT Configuration

In a transistor, IC = 100 mA and IE = 100.2 mA. The value of current gain β is:

100

about 1

500

24BJT Configuration

In a transistor, if β = 100 and collector current is 10 mA, then emitter current IE is:

100 mA

10.1 mA

110 mA

none of the above

25BJT Configuration

The mathematical relationship between β and α is given by:

β = 1 / (1 - α)

β = (1 - α) / α

β = α / (1 - α)

β = α / (1 + α)

26BJT Configuration

The value of common-emitter current gain β for a standard transistor is generally:

less than 1

between 20 and 500

above 500

27BJT Configuration

The most commonly used transistor circuit configuration in amplifier applications is the:

common emitter

common base

common collector

none of the above

28BJT Configuration

The input impedance is highest in which of the following transistor configurations?

common emitter

common collector

common base

none of the above

29BJT Configuration

The output impedance is highest in which of the following transistor configurations?

common emitter

common collector

common base

none of the above

30BJT Configuration

The phase difference between the input and output voltages in a common base amplifier is:

180°

90°

270°

0°

31BJT Configuration

The power gain is highest in which transistor configuration?

common emitter

common base

common collector

none of the above

32BJT Configuration

The phase shift between input and output voltages in a common emitter amplifier is:

0°

180°

90°

270°

33BJT Configuration

Which transistor configuration provides the highest overall combination of voltage and current gain?

common base

common collector

common emitter

none of the above

34BJT Configuration

As the operating temperature of a transistor increases, its internal base-emitter junction resistance:

decreases

increases

remains the same

none of the above

35BJT Configuration

The voltage gain of a transistor connected in common collector (emitter follower) configuration is:

equal to 1

more than 10

more than 100

less than 1

36BJT Configuration

The phase difference between input and output voltages in a common collector amplifier is:

180°

0°

90°

270°

37BJT Configuration

If the value of α is 0.9, what is the corresponding value of current gain β?

0.9

900

38BJT Operation

When transistors are used as electronic switches in digital circuits, they operate exclusively in:

active region

breakdown region

saturation and cutoff regions

linear region

39BJT Operation

The ratio of collector current to emitter current (IC / IE) is called:

beta

theta

alpha

omega

40BJT Operation

A transistor has a β_dc of 250 and a base current IB of 20 µA. The collector current IC is:

500 μA

5 mA

50 mA

5 A

41BJT Biasing

Voltage-divider biasing circuit is widely preferred because it provides:

an unstable Q point

a stable Q point independent of beta variations

a Q point that varies directly with temperature

a Q point with high distortion

42BJT Biasing

To operate properly in the active amplification region, a transistor's base-emitter junction must be forward biased and which junction must be reverse biased?

collector-emitter

base-collector

base-emitter

collector-base

43BJT Biasing

The two endpoints of a DC load line drawn on a transistor's collector characteristic curves determine:

saturation and cutoff points

the operating Q point

the maximum power dissipation curve

the amplification factor

44BJT Configuration

The common-base (CB) configuration is predominantly used to provide:

voltage gain with no current gain

current gain with no voltage gain

very high input impedance

phase inversion

45BJT Operation

In addition to being used as a switching device, an active transistor can function as a:

fixed resistor

tuning device

rectifier

variable current-controlled resistor

46BJT Operation

The transistor parameter β (current gain) represents the ratio:

IC / IB

IC / IE

IB / IE

IE / IB

47BJT Operation

A transistor collector characteristic curve is a plot showing:

IE versus VCE with base current held constant

IC versus VCE with base current (or VBB) held constant

IC versus VC with base bias voltage held constant

IC versus VCC with base bias voltage held constant

48BJT Basics

In low-power through-hole transistor packages (e.g. TO-92), the base terminal lead is usually situated at the:

tab end

middle

right end

stud mount

49BJT Basics

When a silicon transistor is in active forward-bias conduction, the base-emitter voltage VBE is approximately:

0.2 V

0.4 V

0.7 V

1.5 V

50BJT Operation

What is the common-base current gain α when IE = 4.2 mA and IC = 4.0 mA?

16.8

1.05

0.2

0.95

51BJT Biasing

In a negative-supply PNP transistor circuit, the most positive electrical potential in the system is typically:

ground (0 V)

collector voltage VC

base-emitter voltage VBE

negative collector supply -VCC

52BJT Amplifiers

If an input signal of 2 mV produces an output signal of 2 V in a transistor amplifier, the voltage gain Av is:

0.001

0.004

100

1000

53BJT Basics

In an NPN transistor, most of the conduction electrons crossing into the thin base region flow directly:

out of the base terminal

into the collector region

back into the emitter

into the base power supply

54BJT Operation

In active region operation of a bipolar transistor, the collector current is primarily controlled by the:

collector-to-emitter voltage

base current

collector load resistance

internal thermal noise

55BJT Operation

The total emitter current IE in any transistor is given by:

IE - IC

IC + IE

IB + IC

IB - IC

56BJT Amplifiers

A common-collector stage is frequently employed as the output stage before a low-impedance load primarily to:

provide large voltage amplification

provide 180° phase inversion

provide a high-frequency path to bypass RF noise

buffer the voltage amplifiers from the low-resistance load and provide impedance matching for maximum power transfer

57BJT Biasing

For a common-collector (CC) stage to operate in active mode, forward bias must be applied to the:

collector-emitter junction

base-emitter junction

collector-base junction

cathode-anode junction

58BJT Amplifiers

The phase shift between input and output signals in both common-collector and common-base amplifiers is:

270 degrees

180 degrees

90 degrees

0 degrees

59BJT Biasing

If a transistor is biased in the middle of its DC load line, a decrease in transistor current gain β will cause the Q-point to move:

off the load line

nowhere

upward toward saturation

downward toward cutoff

60BJT Amplifiers

Which type of amplification gain is maximized in a common-emitter (CE) transistor configuration?

voltage gain only

current gain only

transresistance gain

power gain

61BJT Operation

Calculate the collector current IC for a CE transistor having β = 100 and base current IB = 30 µA:

30 μA

0.3 μA

3 mA

3 MA