Q.1 Which of the following is a bipolar junction transistor (BJT) type?
NPN
N-channel MOSFET
P-channel JFET
IGBT
Explanation - NPN is a type of BJT. The other options are field-effect or hybrid devices.
Correct answer is: NPN
Q.2 In a silicon NPN transistor, which region is the majority carrier?
Emitter
Base
Collector
All regions
Explanation - In an NPN transistor, electrons (the majority carriers) are injected from the N‑type emitter.
Correct answer is: Emitter
Q.3 What does the term 'forward active region' refer to?
Collector is reverse biased relative to emitter
Both base-emitter and collector-base junctions are forward biased
Base-emitter junction is forward biased, collector-base is reverse biased
All junctions are reverse biased
Explanation - In forward active mode the base‑emitter junction is forward biased and the collector‑base junction is reverse biased.
Correct answer is: Base-emitter junction is forward biased, collector-base is reverse biased
Q.4 Which parameter represents the current gain in common emitter configuration?
β (beta)
α (alpha)
γ (gamma)
δ (delta)
Explanation - β, also called hFE, is the ratio of collector current to base current in common emitter mode.
Correct answer is: β (beta)
Q.5 The transistor's 'cut‑off' region is characterized by which of the following?
High collector current
No collector current
High base current
High emitter current
Explanation - Cut‑off occurs when both junctions are reverse biased, resulting in essentially no collector current.
Correct answer is: No collector current
Q.6 Which of these is a typical purpose of a biasing resistor in a transistor amplifier?
To limit base current
To increase emitter current
To provide AC coupling
To reduce thermal noise
Explanation - Biasing resistors set the DC operating point and limit the base current to safe levels.
Correct answer is: To limit base current
Q.7 What is the typical value range of the Early voltage (VA) for a silicon BJT?
1–5 V
10–20 V
30–50 V
100–200 V
Explanation - Silicon BJTs usually exhibit Early voltages between 10 and 20 volts.
Correct answer is: 10–20 V
Q.8 In a common collector (emitter follower) configuration, the voltage gain is:
Greater than 1
Exactly 1
Less than 1
Negative
Explanation - Emitter follower provides a voltage gain slightly less than unity, typically 0.95–0.99.
Correct answer is: Less than 1
Q.9 Which parameter indicates the maximum safe collector current for a transistor?
I_Cmax
V_CEmax
R_C
C_CE
Explanation - I_Cmax specifies the maximum collector current the device can safely handle.
Correct answer is: I_Cmax
Q.10 The term 'collector-to-emitter breakdown voltage' refers to:
Maximum voltage the transistor can block without conducting
Voltage at which the transistor turns on
Voltage across the base-emitter junction
Voltage that defines the quiescent point
Explanation - V_CEBO is the breakdown voltage across the collector‑emitter when the base is open.
Correct answer is: Maximum voltage the transistor can block without conducting
Q.11 What is the main difference between a PNP and an NPN transistor?
P‑type base vs. N‑type base
Direction of current flow between emitter and collector
Type of semiconductor material
Presence of a built‑in voltage
Explanation - In NPN, current flows from collector to emitter; in PNP it flows from emitter to collector.
Correct answer is: Direction of current flow between emitter and collector
Q.12 Which of the following is a characteristic of a MOSFET compared to a BJT?
High input impedance
Low input impedance
High current gain
Direct current injection
Explanation - MOSFETs have very high input impedance due to the gate being insulated from the channel.
Correct answer is: High input impedance
Q.13 A transistor's 'common base' configuration provides which type of current gain?
Large voltage gain
Large current gain
Large power gain
Large impedance matching
Explanation - Common base offers high current gain but low voltage gain, making it suitable for RF applications.
Correct answer is: Large current gain
Q.14 What role does the 'base-emitter junction' play in a BJT?
It controls the collector current
It acts as a source of carriers for the emitter
It determines the maximum collector voltage
It provides the output signal
Explanation - Biasing the base‑emitter junction controls the minority carriers injected into the collector.
Correct answer is: It controls the collector current
Q.15 The small‑signal model of a BJT includes which of the following elements?
Transconductance (gm) and output resistance (ro)
Capacitance only
Inductance only
Resistor only
Explanation - The hybrid‑π model includes gm, ro, and rπ to represent the transistor's small‑signal behavior.
Correct answer is: Transconductance (gm) and output resistance (ro)
Q.16 Which of the following is the main reason for using a voltage divider for base biasing?
To reduce noise
To set a stable DC bias point
To increase emitter current
To provide AC coupling
Explanation - A voltage divider provides a stable base voltage that is less affected by variations in transistor parameters.
Correct answer is: To set a stable DC bias point
Q.17 What is the purpose of a 'current mirror' in transistor circuits?
To generate a reference voltage
To copy a current from one branch to another
To amplify voltage
To provide load resistance
Explanation - A current mirror uses matched transistors to replicate a current elsewhere in the circuit.
Correct answer is: To copy a current from one branch to another
Q.18 Which parameter is associated with the temperature dependence of a transistor's current gain?
β temperature coefficient
Early voltage variation
Breakdown voltage shift
Collector current limit
Explanation - β tends to decrease with increasing temperature; this coefficient quantifies the change.
Correct answer is: β temperature coefficient
Q.19 The term 'hot spot' in a transistor refers to:
A region with higher current density
An area with higher temperature
The junction where breakdown occurs first
The emitter region only
Explanation - A hot spot is a localized region that dissipates more heat than the rest of the device.
Correct answer is: An area with higher temperature
Q.20 Which of the following is NOT a typical application of a BJT?
Switching
Signal amplification
Power regulation
Digital logic gate
Explanation - Digital logic gates are typically implemented with MOSFETs or TTL, not BJTs.
Correct answer is: Digital logic gate
Q.21 The emitter resistor in a common emitter amplifier provides:
Negative feedback
Positive feedback
Voltage gain
Current amplification only
Explanation - An emitter resistor stabilizes the bias point by providing local negative feedback.
Correct answer is: Negative feedback
Q.22 Which parameter represents the ratio of the collector current to the base current in a BJT?
α (alpha)
β (beta)
γ (gamma)
δ (delta)
Explanation - β (hFE) is defined as I_C / I_B in the common emitter configuration.
Correct answer is: β (beta)
Q.23 In a BJT, the base width is typically:
Wide compared to emitter and collector
Narrower than both emitter and collector
Same width as emitter
Same width as collector
Explanation - The base is deliberately thin to allow carriers to cross efficiently.
Correct answer is: Narrower than both emitter and collector
Q.24 A transistor with a higher current gain is described as:
Low‑beta device
High‑beta device
Low‑g_m device
High‑g_m device
Explanation - Higher β indicates a higher current amplification capability.
Correct answer is: High‑beta device
Q.25 Which of the following best describes the 'collector current' in a BJT?
Minority carriers from the base
Majority carriers from the emitter
Minority carriers from the emitter
Majority carriers from the collector
Explanation - In an NPN, electrons (majority carriers) are injected from the emitter into the collector.
Correct answer is: Majority carriers from the emitter
Q.26 A transistor's 'reverse saturation current' (I_S) is:
Zero in ideal devices
Large in silicon BJTs
Independent of temperature
A small leakage current at reverse bias
Explanation - I_S is the leakage current when the junction is reverse biased; it is very small.
Correct answer is: A small leakage current at reverse bias
Q.27 The 'early effect' in a BJT is due to:
Temperature changes
Base width modulation
Collector current saturation
Emitter injection ratio
Explanation - As V_CE increases, the effective base width decreases, affecting current gain.
Correct answer is: Base width modulation
Q.28 Which component is NOT part of the bias network in a standard common emitter amplifier?
Resistor R1
Resistor R2
Capacitor C1
Inductor L1
Explanation - The bias network typically uses resistors and sometimes a capacitor, not an inductor.
Correct answer is: Inductor L1
Q.29 In a BJT, the term 'emitter degeneration' refers to:
Adding a resistor in series with the emitter
Adding a capacitor across the emitter
Using a PNP emitter instead of NPN
Shorting the emitter to ground
Explanation - Emitter degeneration improves linearity and stability by adding negative feedback.
Correct answer is: Adding a resistor in series with the emitter
Q.30 The maximum power dissipation of a transistor is calculated by:
V_CE × I_C
V_BE × I_B
V_CE × I_B
V_BE × I_C
Explanation - Pmax = V_CE × I_C gives the maximum power the transistor can dissipate.
Correct answer is: V_CE × I_C
Q.31 Which of the following is a typical application for a transistor in the 'push‑pull' configuration?
Audio amplifiers
Power supplies
Digital logic
All of the above
Explanation - Push‑pull stages are used in amplifiers, voltage regulators, and logic drivers.
Correct answer is: All of the above
Q.32 The 'forward current' of a transistor is primarily controlled by:
Base current
Collector voltage
Emitter resistor
Temperature
Explanation - In a BJT, the base current sets the collector current via the current gain.
Correct answer is: Base current
Q.33 Which of the following statements about a 'collector‑to‑emitter breakdown' is correct?
It occurs when the base is forward biased
It occurs when V_CE exceeds a certain threshold
It is the same as avalanche breakdown
It cannot happen in a BJT
Explanation - Collector‑emitter breakdown happens when V_CE exceeds the device's breakdown voltage.
Correct answer is: It occurs when V_CE exceeds a certain threshold
Q.34 Which transistor configuration provides the highest voltage gain?
Common emitter
Common base
Common collector
Differential pair
Explanation - Common emitter offers significant voltage gain, especially with appropriate load resistance.
Correct answer is: Common emitter
Q.35 The 'input impedance' of a common emitter BJT is:
High
Low
Same as the collector impedance
Infinite
Explanation - The base input impedance is relatively low compared to MOSFETs.
Correct answer is: Low
Q.36 In a BJT, the 'emission coefficient' refers to:
Efficiency of carrier injection into the base
Ratio of base to emitter doping
Speed of transistor switching
Temperature coefficient of β
Explanation - The emission coefficient (γ) indicates how effectively carriers cross the emitter‑base junction.
Correct answer is: Efficiency of carrier injection into the base
Q.37 The 'load line' in a transistor circuit is used to determine:
The maximum output voltage
The relationship between I_C and V_CE at equilibrium
The value of the base resistor
The transistor's cutoff frequency
Explanation - The load line graphically shows the operating point for given supply and load.
Correct answer is: The relationship between I_C and V_CE at equilibrium
Q.38 Which of the following is a key benefit of using a Darlington pair?
Very high current gain
Fast switching speed
Low saturation voltage
High input impedance
Explanation - A Darlington pair offers a current gain that is the product of the two transistors' β values.
Correct answer is: Very high current gain
Q.39 What is the main difference between NPN and PNP transistors in terms of polarity of applied voltages for active mode?
NPN uses positive V_CE, PNP uses negative V_CE
NPN uses positive base voltage, PNP uses negative base voltage
Both require the same polarity
Only NPN can be used with negative supply
Explanation - The polarity of base bias is opposite for NPN and PNP devices to forward‑bias the base‑emitter junction.
Correct answer is: NPN uses positive base voltage, PNP uses negative base voltage
Q.40 The 'saturation region' of a BJT is defined by:
Both base‑emitter and base‑collector junctions forward biased
Both base‑emitter and base‑collector junctions reverse biased
Only the collector‑emitter junction forward biased
Only the base‑emitter junction forward biased
Explanation - In saturation, both junctions are forward biased, allowing maximum collector current.
Correct answer is: Both base‑emitter and base‑collector junctions forward biased
Q.41 Which of the following is a parameter that defines the speed of a transistor?
β (beta)
f_T (transition frequency)
I_Cmax
V_CEmax
Explanation - f_T is the frequency at which the current gain drops to unity, indicating transistor speed.
Correct answer is: f_T (transition frequency)
Q.42 The 'base‑to‑collector resistance' (rπ) in the hybrid‑π model primarily represents:
Collector current control
Emitter current control
Base resistance to collector
Collector resistance to emitter
Explanation - rπ models the input resistance looking into the base of a BJT.
Correct answer is: Base resistance to collector
Q.43 In a transistor switch, what is the term for the voltage drop across the collector‑emitter when the transistor is fully on?
Drop‑out voltage
Saturation voltage
Cut‑off voltage
Base‑emitter voltage
Explanation - V_CE(sat) is the small voltage drop when the transistor is fully conducting.
Correct answer is: Saturation voltage
Q.44 Which of these factors most affects the temperature stability of a transistor's β?
Emitter doping concentration
Collector current level
Base width
All of the above
Explanation - Doping, current, and base width all influence β's temperature dependence.
Correct answer is: All of the above
Q.45 A transistor used as a voltage-controlled current source in a common emitter configuration must:
Have a very high β
Have a low emitter resistance
Be biased with a voltage divider
Use a Darlington pair
Explanation - Voltage‑divider bias provides a stable base voltage for current source behavior.
Correct answer is: Be biased with a voltage divider
Q.46 Which of the following is NOT a typical transistor parameter listed on a datasheet?
β (current gain)
f_T (transition frequency)
C_CE (collector‑to‑emitter capacitance)
L_C (collector inductance)
Explanation - Datasheets seldom list inductance; capacitances and frequencies are more common.
Correct answer is: L_C (collector inductance)
Q.47 In a common base configuration, the small‑signal voltage gain is:
Large (>>1)
Approximately 1
Less than 1
Negative
Explanation - Common base offers high voltage gain because the input is at the emitter and the output at the collector.
Correct answer is: Large (>>1)
Q.48 Which of the following is a method to reduce thermal runaway in BJTs?
Use a large emitter resistor
Lower supply voltage
Increase base resistance
Add a small capacitor across collector
Explanation - The emitter resistor provides negative feedback, stabilizing temperature effects.
Correct answer is: Use a large emitter resistor
Q.49 The term 'collector‑to‑emitter voltage swing' refers to:
Maximum voltage across the base
Maximum voltage across collector‑emitter during operation
Voltage between base and collector
Voltage between emitter and ground
Explanation - It represents the dynamic range the transistor can handle in a signal.
Correct answer is: Maximum voltage across collector‑emitter during operation
Q.50 Which parameter defines the transistor's ability to store charge and thus delay switching?
Gate charge
Base‑width
Charge storage time
V_BE
Explanation - Charge storage time indicates how long excess charge remains in the base, slowing transitions.
Correct answer is: Charge storage time
Q.51 In a BJT, the term 'overdrive' typically refers to:
Excess base voltage beyond the threshold
Base voltage less than threshold
Collector current exceeding maximum
Emitter current exceeding maximum
Explanation - Overdrive is the additional base voltage needed to fully saturate the transistor.
Correct answer is: Excess base voltage beyond the threshold
Q.52 The 'β' of a transistor can vary widely between individual devices. This variation is known as:
Process variation
Temperature drift
Manufacturing tolerance
All of the above
Explanation - β can differ due to manufacturing differences, temperature, and other tolerances.
Correct answer is: All of the above
Q.53 Which of these is the primary advantage of using a transistor as a switch rather than a linear amplifier?
Higher linearity
Higher efficiency
Higher current gain
Lower noise
Explanation - Switching transistors spend most time in saturation or cutoff, minimizing power dissipation.
Correct answer is: Higher efficiency
Q.54 The 'base‑to‑collector leakage current' (I_BC) in a BJT is:
Zero at all temperatures
Large compared to I_C
Negligibly small compared to I_B
Independent of voltage
Explanation - I_BC is typically much smaller than the base or collector currents.
Correct answer is: Negligibly small compared to I_B
Q.55 Which type of transistor is best suited for high‑frequency applications?
BJT
MOSFET
JFET
All of the above
Explanation - MOSFETs generally offer higher speed due to lower junction capacitances and no base‑width modulation.
Correct answer is: MOSFET
Q.56 The 'saturation current' (I_S) of a transistor is related to which of the following?
The temperature of the device
The doping level of the emitter
The collector current
The base voltage
Explanation - I_S increases exponentially with temperature, affecting the transistor's I-V relationship.
Correct answer is: The temperature of the device
Q.57 Which of these is a direct consequence of the Early effect?
Collector current becomes independent of collector voltage
Base width increases with collector voltage
Collector current decreases with collector voltage
Output resistance becomes large
Explanation - The Early effect causes the effective base width to shrink, reducing collector current as V_CE increases.
Correct answer is: Collector current decreases with collector voltage
Q.58 When designing a BJT amplifier, the choice of 'collector resistor' primarily determines:
The input impedance
The output impedance
The voltage gain
The current gain
Explanation - The collector resistor sets the load for the transistor, directly affecting voltage gain.
Correct answer is: The voltage gain
Q.59 Which of the following is true about the 'common emitter' transistor configuration?
It provides voltage amplification
It provides current amplification only
It provides power amplification only
It provides no amplification
Explanation - Common emitter is used for voltage and current amplification, with high voltage gain.
Correct answer is: It provides voltage amplification
Q.60 A transistor operating in the linear region is best used for:
Digital logic
Signal amplification
Switching
Power regulation
Explanation - Linear operation allows the transistor to linearly amplify analog signals.
Correct answer is: Signal amplification
Q.61 Which of these is a characteristic of a PNP transistor compared to an NPN?
Higher current gain
Lower V_BE threshold
Opposite polarity of operation
Same collector current
Explanation - PNP transistors require opposite voltage polarities for the same operation modes.
Correct answer is: Opposite polarity of operation
Q.62 In a transistor, what does the 'emitter current' (I_E) represent?
The sum of collector and base currents
Only the current through the emitter
The difference between collector and base currents
The current through the base only
Explanation - I_E = I_B + I_C due to the conservation of charge.
Correct answer is: The sum of collector and base currents
Q.63 Which parameter defines the rate at which a transistor can switch from saturation to cutoff?
Gate charge
Rise time
Fall time
Transition frequency
Explanation - Rise time is the time the transistor takes to go from low to high output, reflecting switching speed.
Correct answer is: Rise time
Q.64 The 'common collector' transistor configuration is often referred to as a(n):
Voltage amplifier
Current amplifier
Emitter follower
Collector follower
Explanation - In common collector, the emitter follows the input voltage with high current gain.
Correct answer is: Emitter follower
Q.65 A transistor's 'cut‑off' point in a circuit is characterized by:
High collector current
Zero collector current
Maximum voltage across collector‑emitter
Zero base current
Explanation - Cut‑off means both junctions are reverse‑biased, resulting in negligible collector current.
Correct answer is: Zero collector current
Q.66 Which of these is a major advantage of using a BJT over a MOSFET for analog amplification?
Higher input impedance
Lower noise
Higher current gain
Simpler biasing
Explanation - BJTs typically provide higher current gain (β) than MOSFETs, beneficial for low‑level signals.
Correct answer is: Higher current gain
Q.67 The 'saturation voltage' (V_CE(sat)) of a transistor is typically:
A few millivolts
A few volts
Zero volts
Negative volts
Explanation - In saturation, V_CE drops to a small value (~0.1–0.3 V).
Correct answer is: A few millivolts
Q.68 In a 'common base' amplifier, the input is applied to which terminal?
Collector
Base
Emitter
All of the above
Explanation - The base is common, so the input is at the emitter.
Correct answer is: Emitter
Q.69 Which of the following parameters is NOT part of the hybrid‑π small‑signal model of a BJT?
gm
ro
Cπ
Lπ
Explanation - The hybrid‑π model includes gm, ro, Cπ, but not an inductance Lπ.
Correct answer is: Lπ
Q.70 The 'collector current' in a BJT is primarily influenced by:
The base voltage
The emitter current
The collector voltage
All of the above
Explanation - Changing V_BE changes I_B, which in turn changes I_C via β.
Correct answer is: The base voltage
Q.71 Which of the following is a common reason for a transistor to go into thermal runaway?
Low emitter resistor
High collector current
High base current
Low supply voltage
Explanation - High collector current increases power dissipation, raising temperature and further increasing current.
Correct answer is: High collector current
Q.72 In a BJT amplifier, the 'output impedance' is primarily determined by:
Collector resistor
Emitter resistor
Base bias network
Emitter current
Explanation - The collector resistor sets the load, which largely defines the output impedance.
Correct answer is: Collector resistor
Q.73 The 'base‑to‑emitter junction' in a BJT is typically forward biased when:
V_BE ≈ 0.6–0.7 V for silicon
V_BE ≈ 1.2 V for silicon
V_CE is high
V_BC is high
Explanation - Forward biasing requires the base to be about 0.6–0.7 V above the emitter for silicon devices.
Correct answer is: V_BE ≈ 0.6–0.7 V for silicon
Q.74 Which of the following is a typical application of a transistor as a 'current source'?
Audio amplifier bias
Digital logic gate
RF oscillator
Voltage regulator
Explanation - Transistor current sources bias amplifiers, ensuring linear operation.
Correct answer is: Audio amplifier bias
Q.75 Which of the following parameters is used to quantify how much voltage changes in the collector for a unit change in base current?
β
gm
ro
α
Explanation - gm (transconductance) relates changes in base current to changes in collector voltage.
Correct answer is: gm
Q.76 A BJT's 'collector‑to‑emitter voltage drop' in active mode is:
Large and constant
Small and constant
Large and variable
Zero
Explanation - V_CE in active mode varies with the load and is typically several volts.
Correct answer is: Large and variable
Q.77 The 'transistor action' refers to:
The process of forward biasing the base-emitter junction
The process of reverse biasing the collector-base junction
The process of controlling current flow in a circuit
The process of heating the transistor
Explanation - Transistor action involves controlling current via biasing and external circuit elements.
Correct answer is: The process of controlling current flow in a circuit
Q.78 In a BJT, the 'base doping' level primarily affects:
Current gain
Input impedance
Switching speed
All of the above
Explanation - Doping influences gain, impedance, and charge storage, thus affecting switching.
Correct answer is: All of the above
Q.79 Which of the following is a primary reason for using a 'common emitter' amplifier in audio circuits?
High input impedance
Low output impedance
High voltage gain
High current gain
Explanation - Common emitter provides significant voltage gain, useful for audio amplification.
Correct answer is: High voltage gain
Q.80 Which of the following best describes 'collector current' in saturation?
Limited by V_CE
Limited by I_B and β
Limited by the supply voltage
Unlimited
Explanation - In saturation, the transistor's collector current is controlled by base current and β, not V_CE.
Correct answer is: Limited by I_B and β
Q.81 Which of the following is an advantage of using a 'Darlington pair' over a single transistor?
Higher current gain
Faster switching
Lower noise
Higher input impedance
Explanation - The combined β of two transistors gives a very high current gain.
Correct answer is: Higher current gain
Q.82 A transistor's 'reverse base‑emitter leakage current' is typically:
Large compared to forward current
Negligible compared to base current
Same as forward current
Zero
Explanation - Reverse leakage is small and usually ignored in most circuits.
Correct answer is: Negligible compared to base current
Q.83 What is the primary function of a 'base‑bias resistor' in a BJT amplifier?
To set the base current
To provide AC coupling
To limit the collector current
To stabilize the emitter voltage
Explanation - The resistor controls how much base current flows, thereby setting the transistor's operating point.
Correct answer is: To set the base current
Q.84 Which of these is true about a transistor's 'cut‑off current'?
It is the maximum collector current
It is the current when V_BC is forward biased
It is the current when both junctions are reverse biased
It is the current when V_BE is high
Explanation - Cut‑off occurs when the transistor is off, resulting in negligible collector current.
Correct answer is: It is the current when both junctions are reverse biased
Q.85 Which of the following is a typical method for reducing distortion in a BJT amplifier?
Using a large emitter resistor
Using a small base resistor
Increasing collector voltage
Removing the bypass capacitor
Explanation - Emitter degeneration linearizes the amplifier and reduces distortion.
Correct answer is: Using a large emitter resistor
Q.86 A transistor's 'saturation voltage' (V_CE(sat)) is lowest when:
The collector current is high
The base current is high
The emitter current is high
The collector voltage is high
Explanation - Higher collector current typically reduces the voltage drop in saturation.
Correct answer is: The collector current is high
Q.87 Which of the following is a correct description of the 'collector current' in a BJT?
It is directly proportional to the emitter current
It is directly proportional to the base current
It is directly proportional to the base voltage
It is independent of the base current
Explanation - Collector current depends on base current via the current gain β.
Correct answer is: It is directly proportional to the base current
Q.88 Which of the following is NOT a typical BJT packaging type?
TO-220
DIP
SOT-223
BGA
Explanation - BGA is not commonly used for discrete BJTs; it is used for integrated circuits.
Correct answer is: BGA
Q.89 In a transistor-based oscillator, the 'feedback resistor' primarily controls:
Amplitude
Frequency
Phase
DC offset
Explanation - Changing the resistor value alters the RC time constant, affecting the oscillation frequency.
Correct answer is: Frequency
Q.90 Which of these is a common method to bias a transistor for a push‑pull amplifier?
Voltage divider bias
Current mirror bias
Self‑biasing
All of the above
Explanation - All listed methods can provide stable bias in push‑pull stages.
Correct answer is: All of the above
Q.91 The 'small‑signal output resistance' of a BJT is mainly influenced by:
Collector current
Emitter resistance
Base bias network
Temperature
Explanation - Higher collector current reduces the output resistance in the hybrid‑π model.
Correct answer is: Collector current
Q.92 Which of the following is a typical value range for a BJT's collector‑to‑emitter breakdown voltage?
0.1–1 V
1–10 V
10–50 V
50–200 V
Explanation - Silicon BJTs usually have V_CEBO in the range of 10–50 volts.
Correct answer is: 10–50 V
Q.93 The 'transistor's 'α' (alpha) is defined as:
I_C / I_B
I_E / I_B
I_C / I_E
I_E / I_C
Explanation - α is the common-base current gain, the ratio of collector to emitter current.
Correct answer is: I_C / I_E
Q.94 A transistor's 'saturation region' is most commonly used in:
Linear amplification
Switching
Voltage regulation
Signal modulation
Explanation - In switching, the transistor is driven into saturation for efficient conduction.
Correct answer is: Switching
Q.95 Which of the following is an advantage of using a MOSFET over a BJT for high‑frequency applications?
Lower input capacitance
Higher current density
Lower saturation voltage
Higher thermal stability
Explanation - MOSFETs have lower input capacitance, enabling higher frequency operation.
Correct answer is: Lower input capacitance
Q.96 What is the main purpose of a 'bypass capacitor' in a transistor amplifier?
To increase input impedance
To provide DC bias
To short the emitter resistor for AC signals
To limit the collector current
Explanation - Bypass capacitor decouples the AC signal from the emitter resistor, improving gain.
Correct answer is: To short the emitter resistor for AC signals
Q.97 In a BJT, the 'collector current' is typically much larger than:
Base current
Emitter current
Collector voltage
Base voltage
Explanation - Because β is usually greater than 1, I_C >> I_B.
Correct answer is: Base current
Q.98 The 'base‑to‑collector leakage current' (I_BC) is often referred to as:
Reverse base‑emitter current
Reverse base‑collector current
Forward base‑collector current
Leakage current
Explanation - I_BC is the tiny current that flows from base to collector when reverse‑biased.
Correct answer is: Reverse base‑collector current
Q.99 Which of these is a typical application of a transistor in a 'class A' amplifier?
High‑power RF transmission
Low‑distortion audio output
Digital switching
Battery regulation
Explanation - Class A amplifiers bias transistors so they conduct throughout the signal cycle, reducing distortion.
Correct answer is: Low‑distortion audio output
Q.100 A 'common emitter' amplifier typically has which of the following input characteristics?
High input impedance
Low input impedance
Medium input impedance
Infinite input impedance
Explanation - The base input presents a low impedance to the signal source.
Correct answer is: Low input impedance
Q.101 The 'collector current' of a BJT is often approximated as:
I_C = β * I_B
I_C = I_B / β
I_C = V_CE / R_C
I_C = I_E - I_B
Explanation - In active mode, collector current is proportional to base current via β.
Correct answer is: I_C = β * I_B
Q.102 Which of the following statements is true about a 'collector‑to‑emitter voltage' in saturation?
It is large and constant
It is small and constant
It is large and variable
It is zero
Explanation - In saturation, V_CE is small (typically ~0.2 V).
Correct answer is: It is small and constant
Q.103 A transistor in the 'active' region is best used for:
Digital logic
Analog amplification
Power switching
Signal detection
Explanation - Active mode allows the transistor to amplify signals linearly.
Correct answer is: Analog amplification
Q.104 Which parameter determines the 'maximum safe operating area' (MOSA) of a transistor?
I_C and V_CE
I_B and V_BE
I_E and V_EC
All of the above
Explanation - MOSA defines the limits of collector current and collector‑emitter voltage.
Correct answer is: I_C and V_CE
Q.105 The 'small‑signal transconductance' (gm) of a BJT is given by:
gm = I_C / V_T
gm = V_T / I_C
gm = I_B / V_T
gm = V_BE / I_C
Explanation - Transconductance is the derivative of collector current with respect to base‑emitter voltage.
Correct answer is: gm = I_C / V_T
Q.106 Which of these is a typical biasing technique to maintain a transistor in the active region?
Voltage divider bias
Fixed current source bias
Self‑biasing with emitter resistor
All of the above
Explanation - Each method stabilizes the Q‑point for linear operation.
Correct answer is: All of the above