BJT Characteristics: Master the Fundamentals of Bipolar Junction Transistors

Question 1

Which of the following is not a commonly used biasing technique for BJTs?

Accepted Answer

Emitter follower

Answer

Base bias

Answer

Voltage divider bias

Answer

Emitter bias

Question 2

In the saturation region of BJT operation, the transistor behaves similarly to:

Accepted Answer

A closed switch

Answer

An open switch

Answer

A linear amplifier

Answer

A current source

Question 3

Which of the following statements about BJT biasing is accurate?

Accepted Answer

Biasing establishes a stable operating point for the transistor.

Answer

Biasing is not essential for BJT operation.

Answer

Biasing can be achieved exclusively through base bias.

Answer

Biasing always reduces the gain of the transistor.

Question 4

Which of the following is NOT a region of operation for a BJT?

Accepted Answer

Inverse-active

Answer

Saturation

Answer

Cut-off

Answer

Forward-active

Question 5

In a common-emitter amplifier, the input signal is applied to:

Accepted Answer

Base

Answer

Collector

Answer

Emitter

Answer

Both base and emitter

Question 6

The Early effect refers to the:

Accepted Answer

Increase in collector-emitter voltage due to an increase in collector current

Answer

Decrease in collector current due to a decrease in base current

Answer

Change in base-emitter voltage due to a change in collector voltage

Answer

Variation in output voltage due to changes in input impedance

Question 7

The current gain of a BJT in the forward-active region is typically:

Accepted Answer

Greater than 1

Answer

Less than 1

Answer

Equal to 1

Answer

Dependent on the type of BJT

Question 8

A BJT can be modeled as:

Accepted Answer

A current-controlled current source

Answer

A voltage-controlled current source

Answer

A current-controlled voltage source

Answer

A voltage-controlled voltage source

Question 9

How does the common-base current gain (alpha) influence collector current in a BJT? Express this relationship mathematically.

Accepted Answer

Alpha directly affects collector current, with a higher alpha leading to a higher collector current.

Answer

Alpha has no effect on collector current.

Answer

Alpha has an inverse relationship with collector current, meaning a higher alpha results in a lower collector current.

Question 10

What is the typical range of the forward current gain (β) of a BJT?

Accepted Answer

Greater than 1

Answer

Less than 1

Answer

Equal to 1

Answer

Negative

Question 11

Which biasing technique ensures that the transistor operates in the active region while minimizing temperature sensitivity?

Accepted Answer

Voltage divider bias

Answer

Fixed bias

Answer

Emitter bias

Answer

Collector feedback bias

Question 12

In a common-emitter amplifier, the input signal is applied to the:

Accepted Answer

Base

Answer

Collector

Answer

Emitter

Answer

Gate

Question 13

Which of the following is NOT a factor that affects the base-emitter voltage of a BJT?

Accepted Answer

Collector current

Answer

Base current

Answer

Emitter current

Answer

Temperature

Question 14

Which of the following statements about BJTs is true?

Accepted Answer

They have a higher current-carrying capacity than FETs.

Answer

They have a lower input impedance than FETs.

Answer

They can operate at higher frequencies than FETs.

Answer

Their noise figure is higher than that of FETs.

Question 15

In a transistor operating in the saturation region, the:

Accepted Answer

Collector-emitter voltage is low.

Answer

Collector-emitter voltage is high.

Answer

Base-emitter voltage is high.

Answer

Base-collector voltage is low.

Question 16

The current gain of a BJT in the active region is known as:

Accepted Answer

Beta

Answer

Alpha

Answer

Gamma

Answer

Delta

Question 17

In a common-emitter configuration, the input signal is applied to:

Accepted Answer

Base terminal

Answer

Emitter terminal

Answer

Collector terminal

Answer

Gate terminal

Question 18

In a BJT amplifier circuit, the purpose of a bypass capacitor connected across the emitter resistor is to:

Accepted Answer

Improve the frequency response

Answer

Increase the AC gain

Answer

Reduce the DC gain

Answer

Prevent thermal runaway

Question 19

Which of the following applications is NOT suitable for BJTs?

Accepted Answer

Digital logic circuits

Answer

Audio amplifiers

Answer

Power supplies

Answer

High-frequency oscillators

Question 20

Which biasing technique is predominantly used to establish a stable operating point for a BJT?

Accepted Answer

DC biasing

Answer

Transistor biasing

Answer

Capacitive coupling

Answer

AC coupling

Question 21

What is the primary purpose of utilizing a load line in BJT analysis?

Accepted Answer

To determine the transistor's operating point

Answer

To optimize the transistor's frequency response

Answer

To measure the transistor's voltage gain

Answer

To calculate the transistor's power dissipation

Question 22

In a saturated BJT, which regions are forward-biased?

Accepted Answer

Both the emitter-base and collector-base junctions

Answer

Only the collector-base junction

Answer

Neither the emitter-base nor collector-base junctions

Answer

Only the emitter-base junction

Question 23

What is the main application of a BJT?

Accepted Answer

Amplifying electrical signals

Answer

Filtering electrical signals

Answer

Rectifying electrical signals

Answer

Regulating electrical signals

Question 24

In the common-emitter configuration of a BJT, the current gain is known as:

Accepted Answer

β (beta)

Answer

α (alpha)

Answer

VBE

Answer

hFE

Question 25

The Early effect in BJTs leads to:

Accepted Answer

A decrease in collector current with increasing collector-emitter voltage

Answer

No change in collector current with increasing collector-emitter voltage

Answer

An increase in collector current with increasing collector-emitter voltage

Question 26

Which BJT operating region has a very low collector current?

Accepted Answer

Cutoff region

Answer

Saturation region

Answer

Reverse active region

Answer

Active region

Question 27

In the common-base configuration of a BJT, the current gain is:

Accepted Answer

Less than one

Answer

Greater than one

Answer

Equal to one

Answer

Zero

Question 28

Which statement about BJT biasing is accurate?

Accepted Answer

Biasing establishes the transistor's operating point.

Answer

Biasing only impacts the base current.

Answer

Biasing has no effect on transistor functionality.

Question 29

The hFE parameter of a BJT measures:

Accepted Answer

DC current gain

Answer

Voltage gain

Answer

AC current gain

Answer

Power gain

Question 30

What is the relationship between alpha (α) and beta (β) in a BJT?

Accepted Answer

β = α / (1 - α)

Answer

α = 1 / β

Answer

β = 1 / α

Answer

α = β / (1 + β)

Question 31

What is the primary purpose of biasing in BJT circuits?

Accepted Answer

To establish a stable operating point

Answer

To reduce noise

Answer

To prevent thermal runaway

Answer

To increase current gain

Question 32

What is the effect of increasing the collector current (Ic) in a BJT?

Accepted Answer

Increased emitter current (Ie)

Answer

No change in base current

Answer

Decreased collector current

Answer

Decreased base current (Ib)

Question 33

Which mode of BJT operation is characterized by a negligible collector current (Ic)?

Accepted Answer

Cutoff

Answer

Saturation

Answer

Active

Question 34

Which factor primarily affects the breakdown voltage (BV) of a BJT?

Accepted Answer

Doping concentration

Answer

Collector current

Answer

Base width

Answer

Emitter area

Question 35

Which of the following is an advantage of using a BJT over a FET?

Accepted Answer

Higher current handling capability

Answer

Higher input impedance

Answer

Lower power consumption

Answer

Lower noise

Question 36

What is the function of a heat sink in a BJT circuit?

Accepted Answer

To dissipate excess heat

Answer

To increase current gain

Answer

To prevent thermal runaway

Answer

To reduce noise

Question 37

In a common-emitter BJT configuration, how does the collector current (IC) relate to the base current (IB)?

Accepted Answer

The collector current is approximately beta (β) times the base current.

Answer

The collector current is equal to the base current.

Answer

The base current is always larger than the collector current.

Question 38

What is the main function of the emitter in a BJT?

Accepted Answer

To inject majority charge carriers into the base region.

Answer

To act as a collector of the majority charge carriers.

Answer

To provide a path for current flow between the base and collector.

Answer

To collect minority charge carriers from the base region.

Question 39

Which biasing method is most commonly used for achieving a stable operating point in a BJT amplifier?

Accepted Answer

Voltage divider biasing

Answer

Emitter feedback biasing

Answer

Fixed biasing

Answer

Collector feedback biasing

Question 40

In a common-emitter configuration, if the base-emitter junction is forward-biased and the base-collector junction is reverse-biased, the BJT is operating in which region?

Accepted Answer

Active region

Answer

Cutoff region

Answer

Saturation region

Question 41

What is the relationship between alpha (α) and beta (β) in a BJT?

Accepted Answer

Beta is approximately equal to alpha divided by (1-alpha).

Answer

Alpha and beta are independent of each other.

Answer

Alpha is always greater than beta.

Question 42

Which of the following correctly identifies the main operating regions of a BJT?

Accepted Answer

Active, Saturation, and Cutoff

Answer

Ohmic, Active, and Passive

Answer

Linear, Non-linear, and Exponential

Answer

Forward, Reverse, and Breakdown

Question 43

The current gain (β) of a BJT is defined as the ratio of:

Accepted Answer

Collector current (IC) to base current (IB)

Answer

Base current (IB) to collector current (IC)

Answer

Emitter current (IE) to base current (IB)

Answer

Collector current (IC) to emitter current (IE)

Question 44

In a common-emitter configuration, increasing the base current will cause the collector current to:

Accepted Answer

Increase

Answer

Become zero

Answer

Decrease

Answer

Remain the same

Question 45

What is the primary purpose of biasing a transistor?

Accepted Answer

To establish a stable operating point

Answer

To reduce power dissipation

Answer

To prevent thermal runaway

Answer

To increase the current gain

Question 46

Which biasing technique provides stable operating point despite variations in transistor parameters?

Accepted Answer

Voltage divider bias

Answer

Fixed bias

Answer

Emitter bias

Answer

Collector feedback bias

Question 47

The Early effect in a BJT refers to the variation of which parameter with collector-emitter voltage?

Accepted Answer

Base width

Answer

Base current

Answer

Emitter current

Question 48

A BJT is said to be in saturation when:

Accepted Answer

Both the base-emitter and base-collector junctions are forward biased.

Answer

The base-emitter junction is forward biased, and the base-collector junction is reverse biased.

Answer

Both the base-emitter and base-collector junctions are reverse biased.

Question 49

The input resistance of a common-emitter amplifier is primarily determined by the:

Accepted Answer

Base-emitter junction resistance

Answer

Collector-emitter junction resistance

Answer

Collector resistor

Answer

Emitter resistor

Question 50

Which of the following is NOT a typical application of BJTs?

Accepted Answer

High-power rectification

Answer

Oscillation

Answer

Switching

Answer

Amplification