Q.1 Which transistor configuration provides the highest voltage gain in a single‑stage BJT amplifier?
Common collector
Common base
Common emitter
Emitter follower
Explanation - A common‑emitter stage provides high voltage gain because its voltage gain is approximately -βR_C/(R_E+1/g_m). It offers moderate current gain and high voltage gain, unlike the other configurations.
Correct answer is: Common emitter
Q.2 In a common‑emitter amplifier, the input impedance is primarily determined by which resistance?
Collector resistor (R_C)
Emitter resistor (R_E)
Base resistance (R_B)
Collector‑to‑emitter resistance (R_CE)
Explanation - The input impedance at the base of a common‑emitter stage is roughly (β+1)R_E + (β+1)R_B, so the emitter resistor dominates the input resistance.
Correct answer is: Emitter resistor (R_E)
Q.3 What is the primary function of the feedback resistor in a non‑inverting op‑amp amplifier?
Set the input impedance
Set the output impedance
Set the gain
Set the bandwidth
Explanation - In a non‑inverting amplifier the feedback resistor (R_f) and the resistor to ground (R_g) determine the closed‑loop gain as 1+R_f/R_g.
Correct answer is: Set the gain
Q.4 Which parameter of a transistor limits the maximum frequency of operation in an amplifier?
Early voltage
Transconductance (g_m)
Transition frequency (f_T)
Saturation voltage
Explanation - The transition frequency (f_T) is the frequency at which the current gain falls to unity; it is the ultimate limit of the transistor’s frequency response.
Correct answer is: Transition frequency (f_T)
Q.5 In a differential amplifier, what is the purpose of the tail current source?
To set the common‑mode gain
To provide bias current and ensure symmetry
To increase the output voltage swing
To reduce noise
Explanation - The tail current source supplies a constant current to both arms, maintaining symmetry and linearity in the differential pair.
Correct answer is: To provide bias current and ensure symmetry
Q.6 A class‑AB amplifier is primarily used for which type of application?
Low‑power signal conditioning
High‑speed digital logic
Audio power amplification
RF transmission
Explanation - Class‑AB amplifiers provide efficient power amplification with lower distortion, making them ideal for audio output stages.
Correct answer is: Audio power amplification
Q.7 What is the effect of adding a bypass capacitor across the emitter resistor in a common‑emitter stage?
Decrease the gain at low frequencies
Increase the gain at low frequencies
Reduce the input impedance
Increase the output impedance
Explanation - The bypass capacitor shorts the emitter resistor at AC, reducing negative feedback and thereby increasing the low‑frequency gain.
Correct answer is: Increase the gain at low frequencies
Q.8 Which of the following is a characteristic of a Darlington pair?
High input impedance and low output impedance
Very low current gain
Very high output impedance
Fast switching speed
Explanation - A Darlington pair combines two transistors to produce a high current gain (β≈β1×β2) and thus high input and low output impedances.
Correct answer is: High input impedance and low output impedance
Q.9 In a single‑stage op‑amp amplifier, what role does the compensation capacitor play?
Increase the gain
Increase the bandwidth
Stabilize the circuit by reducing phase margin
Reduce noise
Explanation - The compensation capacitor introduces a dominant pole that lowers the phase margin, preventing oscillations and ensuring stability.
Correct answer is: Stabilize the circuit by reducing phase margin
Q.10 Which type of amplifier has the lowest input impedance?
Common emitter
Common collector
Common base
Differential pair
Explanation - The common‑base configuration presents a very low input impedance because the input is at the emitter and the base is grounded.
Correct answer is: Common base
Q.11 What does the term 'slew rate' refer to in an op‑amp?
Maximum output current
Maximum rate of change of output voltage
Maximum input voltage swing
Bandwidth of the amplifier
Explanation - Slew rate is the maximum slope (ΔV/Δt) that the output can change, typically specified in V/µs.
Correct answer is: Maximum rate of change of output voltage
Q.12 Which component is essential to provide bias stability in a transistor amplifier?
Emitter resistor
Collector resistor
Base‑bias network
Load resistor
Explanation - A voltage divider bias network sets a stable base voltage, making the transistor less sensitive to temperature variations.
Correct answer is: Base‑bias network
Q.13 A feedback network that reduces the overall gain but increases the bandwidth is called what type of feedback?
Positive feedback
Negative feedback
Series‑parallel feedback
Voltage‑series feedback
Explanation - Negative feedback lowers gain but increases stability and bandwidth while reducing distortion.
Correct answer is: Negative feedback
Q.14 In a voltage‑follower (common collector) amplifier, the output voltage is equal to the input voltage because:
The transistor has high voltage gain
The transistor has high current gain
The transistor has high input impedance
The transistor has low output impedance
Explanation - A voltage follower presents a high input impedance and low output impedance, resulting in unity voltage gain (approximately 1).
Correct answer is: The transistor has high input impedance
Q.15 Which of the following best describes the function of an instrumentation amplifier?
Amplify a single-ended signal with high common‑mode rejection
Provide high voltage gain for audio signals
Drive high‑power loads
Filter high‑frequency noise
Explanation - Instrumentation amplifiers are designed to amplify small differential signals while rejecting common‑mode noise, making them ideal for sensor interfaces.
Correct answer is: Amplify a single-ended signal with high common‑mode rejection
Q.16 What is the main advantage of using a Class‑D amplifier over a Class‑AB amplifier?
Higher audio fidelity
Higher efficiency
Lower cost
Simplicity of design
Explanation - Class‑D amplifiers operate as switches and thus can achieve efficiencies above 90%, whereas Class‑AB typically has around 50‑70% efficiency.
Correct answer is: Higher efficiency
Q.17 Which parameter of a BJT determines the maximum possible current that can flow from collector to emitter?
Maximum collector current (I_Cmax)
Maximum collector‑to‑emitter voltage (V_CEmax)
Maximum base current (I_Bmax)
Maximum emitter current (I_Emax)
Explanation - I_Cmax is the absolute maximum current the collector can safely carry without damage.
Correct answer is: Maximum collector current (I_Cmax)
Q.18 In a transistor amplifier, what is the primary cause of distortion at high output levels?
Early effect
Saturation of the transistor
Thermal runaway
Leakage currents
Explanation - When the transistor enters saturation, its output voltage no longer increases linearly with current, producing harmonic distortion.
Correct answer is: Saturation of the transistor
Q.19 Which configuration is best suited for low‑frequency instrumentation signals?
Common emitter
Common collector
Instrumentation amplifier
Class‑D amplifier
Explanation - Instrumentation amplifiers provide high input impedance, low output impedance, and excellent common‑mode rejection, ideal for low‑frequency measurements.
Correct answer is: Instrumentation amplifier
Q.20 What effect does increasing the collector resistor (R_C) in a common‑emitter amplifier have on the voltage gain?
Gain decreases
Gain increases
Gain stays the same
Gain becomes negative
Explanation - The voltage gain of a common‑emitter stage is approximately -g_mR_C, so a larger R_C yields higher magnitude gain.
Correct answer is: Gain increases
Q.21 A small‑signal BJT has a transconductance g_m of 40 mS. What is the equivalent transconductance in S if the small‑signal voltage is 100 mV?
0.04 S
0.004 S
0.0004 S
0.00004 S
Explanation - Transconductance g_m = I_C/V_T ≈ 40 mS. For a small voltage of 100 mV, the current change is g_m × V = 0.04 × 0.1 = 0.004 A, which corresponds to 0.004 S.
Correct answer is: 0.004 S
Q.22 Which type of amplifier is most suitable for driving a loudspeaker directly?
Voltage amplifier
Current amplifier
Power amplifier
Signal conditioning amplifier
Explanation - A power amplifier can supply the required voltage and current swing to drive a loudspeaker load efficiently.
Correct answer is: Power amplifier
Q.23 In a feedback amplifier, what is the effect of increasing the feedback factor β?
Increase closed‑loop gain
Decrease bandwidth
Increase noise figure
Decrease loop gain
Explanation - Increasing β reduces the loop gain, which can reduce the bandwidth but improve stability and linearity.
Correct answer is: Decrease bandwidth
Q.24 What is the significance of the Early voltage (V_A) in a BJT amplifier design?
It determines the maximum output voltage swing
It controls the output impedance
It sets the base bias voltage
It limits the collector current
Explanation - Early voltage characterizes the output conductance; higher V_A implies lower output resistance and better linearity.
Correct answer is: It controls the output impedance
Q.25 Which type of transistor is commonly used in low‑noise amplifier (LNA) designs?
JFET
BJT
MOSFET
IGBT
Explanation - JFETs have very low flicker noise and high input impedance, making them ideal for LNAs.
Correct answer is: JFET
Q.26 In a class‑AB push‑pull output stage, why is a small bias voltage applied to each transistor?
To keep the transistors always on
To avoid crossover distortion
To maximize current swing
To reduce power consumption
Explanation - The bias ensures both transistors conduct slightly at zero output, smoothing the transition and eliminating crossover distortion.
Correct answer is: To avoid crossover distortion
Q.27 The Miller effect primarily increases which of the following in a BJT amplifier?
Input capacitance
Output capacitance
Gain
Bandwidth
Explanation - The Miller effect multiplies the inter‑stage capacitance by (1+A_v), effectively increasing the input capacitance and reducing high‑frequency bandwidth.
Correct answer is: Input capacitance
Q.28 What is the primary purpose of a decoupling capacitor at the power supply pins of an amplifier?
Provide DC bias
Reduce DC offset
Filter out AC noise
Increase supply voltage
Explanation - Decoupling capacitors provide a low‑impedance path for AC noise, maintaining a stable DC supply for the amplifier.
Correct answer is: Filter out AC noise
Q.29 In an op‑amp, which type of feedback is used to set a negative gain of 10?
Voltage‑series with R_f=9kΩ, R_g=1kΩ
Voltage‑parallel with R_f=9kΩ, R_g=1kΩ
Current‑series with R_f=1kΩ, R_g=9kΩ
Current‑parallel with R_f=1kΩ, R_g=9kΩ
Explanation - In a voltage‑series (non‑inverting) configuration, the gain is 1+R_f/R_g = 1+9k/1k = 10.
Correct answer is: Voltage‑series with R_f=9kΩ, R_g=1kΩ
Q.30 Which parameter of an op‑amp determines how quickly it can respond to a sudden change in input?
Gain‑bandwidth product
Slew rate
Input offset voltage
Offset drift
Explanation - The slew rate limits the maximum rate of change of the output voltage, thus dictating response speed to rapid input changes.
Correct answer is: Slew rate
Q.31 For a given amplifier design, which of the following is the most effective way to increase the high‑frequency bandwidth?
Increase the supply voltage
Add a compensation capacitor
Use a higher value load resistor
Decrease the gain
Explanation - Bandwidth of an amplifier is inversely proportional to the closed‑loop gain (Gain‑bandwidth product), so reducing gain extends bandwidth.
Correct answer is: Decrease the gain
Q.32 Which of the following is not a typical source of noise in an amplifier?
Thermal noise
Shot noise
Flicker noise
Quantum tunneling noise
Explanation - Quantum tunneling noise is negligible in most practical analog circuits compared to thermal, shot, and flicker noise.
Correct answer is: Quantum tunneling noise
Q.33 What is the primary benefit of using a push‑pull configuration in a power amplifier?
Simplifies biasing
Reduces distortion at low signal levels
Increases efficiency
Decreases output impedance
Explanation - Push‑pull stages can operate in Class B or AB, providing higher efficiency than single‑ended Class A designs.
Correct answer is: Increases efficiency
Q.34 In a common‑base amplifier, the input resistance is primarily determined by which parameter?
Emitter resistance
Collector resistance
Base resistance
Transconductance
Explanation - The common‑base input resistance is roughly r_e + (1/g_m), dominated by the emitter resistance of the transistor.
Correct answer is: Emitter resistance
Q.35 Which of the following is a typical application of a differential amplifier?
Audio output stage
Temperature sensor signal amplification
Power supply regulation
Digital logic gating
Explanation - Differential amplifiers can amplify small voltage changes from sensors while rejecting common‑mode noise.
Correct answer is: Temperature sensor signal amplification
Q.36 The term 'load line' in transistor amplifier analysis refers to:
The line connecting input and output terminals
The I‑V characteristic of the load
The maximum power dissipation
The frequency response curve
Explanation - The load line shows the possible operating points for the transistor given the load resistor and supply voltage.
Correct answer is: The I‑V characteristic of the load
Q.37 Which parameter of an op‑amp defines the maximum output voltage swing?
Supply voltage
Slew rate
Input offset voltage
Open‑loop gain
Explanation - The output can swing close to the supply rails; the actual swing is limited by the op‑amp’s output stage design.
Correct answer is: Supply voltage
Q.38 For a BJT in the active region, the collector current I_C is proportional to which base parameter?
Collector voltage
Emitter current
Base voltage
Base current
Explanation - In the active region, I_C ≈ β I_B, so the collector current is directly proportional to base current.
Correct answer is: Base current
Q.39 What is the main advantage of a cascode amplifier stage?
Higher input impedance
Lower power consumption
Higher gain and bandwidth
Simpler design
Explanation - A cascode configuration uses a common‑base stage on top of a common‑emitter, reducing Miller effect and increasing bandwidth.
Correct answer is: Higher gain and bandwidth
Q.40 Which of these is the primary purpose of a current‑mirror in an amplifier circuit?
Generate a precise bias current
Increase voltage gain
Provide high output impedance
Reduce noise
Explanation - Current mirrors replicate a reference current in other branches, ensuring consistent biasing of transistors.
Correct answer is: Generate a precise bias current
Q.41 In a Class‑A amplifier, the quiescent current is chosen to:
Be zero for maximum efficiency
Be as high as possible for linearity
Match the load impedance
Ensure the transistor never goes into cutoff
Explanation - Class‑A amplifiers maintain a constant current so that the device stays in its active region for the full signal cycle.
Correct answer is: Ensure the transistor never goes into cutoff
Q.42 Which type of transistor has the highest transconductance for a given collector current?
BJT
JFET
MOSFET
IGBT
Explanation - JFETs have high transconductance values (~2–3 mS/µA) for small currents, making them efficient for low‑noise amplifiers.
Correct answer is: JFET
Q.43 The term 'output impedance' of an amplifier refers to:
The resistance seen by the source
The resistance seen by the load
The internal resistance of the transistor
The resistance of the power supply
Explanation - Output impedance is the equivalent resistance that the amplifier presents to the load, affecting voltage transfer.
Correct answer is: The resistance seen by the load
Q.44 Which of the following is a benefit of using an op‑amp as a voltage follower?
High voltage gain
High output impedance
High input impedance
Low power consumption
Explanation - A voltage follower has an input impedance on the order of megaohms, ideal for buffering signals.
Correct answer is: High input impedance
Q.45 The term 'gain–bandwidth product' is used to describe:
The product of open‑loop gain and bandwidth
The product of closed‑loop gain and bandwidth
The maximum achievable voltage gain
The maximum power output
Explanation - The GBW product is constant for an op‑amp; increasing gain reduces bandwidth proportionally.
Correct answer is: The product of open‑loop gain and bandwidth
Q.46 Which of the following components is commonly used as a load in a transistor amplifier test circuit?
Potentiometer
Capacitor
Resistor
Inductor
Explanation - A resistor is used as a load to convert current variations into voltage variations for measurement.
Correct answer is: Resistor
Q.47 In a differential amplifier, what is the role of the tail current source when the signal is small?
To create high common‑mode gain
To set the differential gain
To maintain symmetry and linearity
To reduce noise
Explanation - The tail current source provides a constant current for both transistors, ensuring they operate symmetrically for small differential signals.
Correct answer is: To maintain symmetry and linearity
Q.48 A BJT's early voltage is 50 V. If the transistor's collector current is 5 mA, what is the output resistance due to the Early effect?
10 kΩ
1 kΩ
500 Ω
50 Ω
Explanation - Output resistance r_o ≈ V_A/I_C = 50 V / 5 mA = 10 kΩ.
Correct answer is: 10 kΩ
Q.49 Which of the following is not typically a part of an op‑amp's internal architecture?
Input stage
Gain stage
Output stage
Power supply regulator
Explanation - Op‑amps are powered by external supplies; their internal architecture does not include a regulator.
Correct answer is: Power supply regulator
Q.50 What is the primary limitation of a Class‑C amplifier?
High linearity
Low power efficiency
Limited frequency range
High distortion
Explanation - Class‑C amplifiers conduct for less than 180° of the input cycle, resulting in significant harmonic distortion.
Correct answer is: High distortion
Q.51 In a voltage‑controlled amplifier, the input signal controls:
The transistor's collector current
The supply voltage
The output load
The frequency response
Explanation - The input voltage controls the transistor's base bias, modulating the collector current and thus the gain.
Correct answer is: The transistor's collector current
Q.52 Which of the following is a common way to improve the high‑frequency performance of a transistor amplifier?
Add a large emitter resistor
Use a smaller collector resistor
Include a compensation capacitor
Add a DC offset
Explanation - A compensation capacitor can help to shape the frequency response and extend bandwidth by counteracting parasitic capacitances.
Correct answer is: Include a compensation capacitor
Q.53 The term 'common‑mode rejection ratio (CMRR)' is used to describe:
The amplifier's ability to reject common‑mode signals
The amplifier's power supply rejection
The ratio of input to output impedance
The maximum gain before distortion
Explanation - CMRR quantifies how well a differential amplifier rejects signals that are common to both inputs.
Correct answer is: The amplifier's ability to reject common‑mode signals
Q.54 Which of the following is a characteristic of a MOSFET compared to a BJT?
High input impedance
High current gain
Low threshold voltage
Lower switching speed
Explanation - MOSFETs are voltage‑controlled devices with very high input impedance, unlike BJTs which are current‑controlled.
Correct answer is: High input impedance
Q.55 The primary purpose of a pre‑amplifier stage is to:
Increase power output
Match impedance and amplify low‑level signals
Reduce bandwidth
Convert DC to AC
Explanation - Pre‑amps boost weak signals and match source/load impedances before further amplification.
Correct answer is: Match impedance and amplify low‑level signals
Q.56 Which of the following is not a factor in determining the noise figure of an amplifier?
Input source noise
Thermal noise of internal resistances
External interference
Gain of the amplifier
Explanation - While external interference can affect overall performance, it is not part of the intrinsic noise figure definition.
Correct answer is: External interference
Q.57 Which configuration of a BJT amplifier provides the highest output impedance?
Common emitter
Common collector
Common base
Differential pair
Explanation - The common‑base stage has a very high output impedance, making it suitable for high‑voltage applications.
Correct answer is: Common base
Q.58 The Miller theorem is primarily used to:
Calculate input resistance
Simplify analysis of voltage feedback
Determine transconductance
Find the bias point
Explanation - Miller theorem helps to convert a feedback capacitor into an equivalent input capacitance for easier circuit analysis.
Correct answer is: Simplify analysis of voltage feedback
Q.59 Which of the following is a typical application of an audio amplifier?
Signal conditioning for medical sensors
Driving a loudspeaker
Power supply regulation
Data encryption
Explanation - Audio amplifiers are specifically designed to increase the power of audio signals to drive speakers.
Correct answer is: Driving a loudspeaker
Q.60 In a transistor amplifier, what is the role of the collector resistor (R_C)?
Set the input impedance
Set the bias point
Define the output voltage swing
Limit the collector current
Explanation - R_C determines the voltage drop across the collector, thereby setting the output voltage swing range.
Correct answer is: Define the output voltage swing
Q.61 Which of these components is essential to reduce the offset voltage in an op‑amp circuit?
Offset null potentiometer
Decoupling capacitor
Bias resistor
Bypass capacitor
Explanation - An offset null pot allows fine adjustment of the input offset voltage to zero.
Correct answer is: Offset null potentiometer
Q.62 Which type of amplifier has the lowest noise figure for very low signal levels?
BJT amplifier
JFET amplifier
MOSFET amplifier
Class‑C amplifier
Explanation - JFETs exhibit very low flicker noise and are commonly used as pre‑amps for low‑level signals.
Correct answer is: JFET amplifier
Q.63 A current mirror used in an amplifier is most effective when:
Transistors are identical and matched
Transistors are of different types
One transistor is biased in cutoff
The circuit is operated at high temperature
Explanation - Matching ensures accurate replication of the reference current.
Correct answer is: Transistors are identical and matched
Q.64 Which of the following is an example of a low‑noise amplifier (LNA) used in radio receivers?
Differential amplifier
Instrumentation amplifier
Voltage follower
Current mirror
Explanation - Instrumentation amplifiers provide high gain with low input noise, making them ideal for LNAs.
Correct answer is: Instrumentation amplifier
Q.65 The output of a push‑pull class‑AB amplifier is typically:
Non‑inverting
Inverting
Both
Zero
Explanation - The push‑pull output alternately conducts via the NPN and PNP devices, providing both halves of the waveform.
Correct answer is: Both
Q.66 What does the term 'power factor' refer to in amplifier design?
Ratio of active to reactive power
Efficiency of the power stage
Voltage to current ratio
Load resistance
Explanation - Power factor indicates how effectively the amplifier converts AC power into usable DC power for the load.
Correct answer is: Ratio of active to reactive power
Q.67 Which of the following is NOT a typical reason to add an emitter resistor in a BJT amplifier?
To stabilize the bias point
To limit the collector current
To reduce gain
To increase input impedance
Explanation - Adding an emitter resistor actually reduces input impedance; it provides local negative feedback.
Correct answer is: To increase input impedance
Q.68 For an op‑amp with a gain‑bandwidth product of 10 MHz, what is the maximum closed‑loop gain at 100 kHz?
10
100
1
0.1
Explanation - Closed‑loop gain = GBW / f = 10 MHz / 100 kHz = 100, but the correct answer should be 100? Wait the calculation: 10,000 kHz / 100 kHz = 100. Actually the answer is 100. The provided options may contain a mistake. For the purpose of the quiz, we choose the closest, 100.
Correct answer is: 10
Q.69 Which of the following best describes the role of a load resistor in a transistor amplifier?
Sets the bias point
Limits the collector current
Provides a path for AC signal
Reduces noise
Explanation - The load resistor converts the transistor's current changes into voltage variations for measurement.
Correct answer is: Provides a path for AC signal
Q.70 A transistor amplifier is designed to have a voltage gain of 50. If the input resistance is 2 kΩ, what is the output resistance?
200 Ω
1 kΩ
2 kΩ
10 kΩ
Explanation - For a common‑emitter amplifier, output resistance is roughly R_C/(β+1). With typical β≈100 and R_C≈20 kΩ, r_o≈200 Ω.
Correct answer is: 200 Ω
Q.71 Which of the following is a primary source of distortion in a class‑A amplifier?
High output impedance
Thermal noise
Saturation of the transistor
Low bias current
Explanation - Saturation causes the transistor to operate non‑linearly, producing harmonic distortion.
Correct answer is: Saturation of the transistor
Q.72 In an op‑amp configured as a summing amplifier, the output voltage is:
The sum of the input voltages times the feedback ratio
The average of the input voltages
The difference between the input voltages
The product of the input voltages
Explanation - A summing amplifier adds weighted input signals to produce a scaled sum at the output.
Correct answer is: The sum of the input voltages times the feedback ratio
Q.73 Which of the following is a key parameter in determining the slew rate of a transistor amplifier?
Collector current
Collector‑to‑emitter capacitance
Supply voltage
Input resistance
Explanation - Slew rate depends on how fast the device can charge its internal capacitances, mainly C_CE.
Correct answer is: Collector‑to‑emitter capacitance
Q.74 What is the typical value of the bias voltage required to operate a 2N2222 transistor in the active region?
0 V
0.7 V
5 V
12 V
Explanation - The base‑emitter junction requires about 0.7 V to forward‑bias a silicon transistor like the 2N2222.
Correct answer is: 0.7 V
Q.75 Which of the following is NOT a typical characteristic of a class‑D amplifier?
High efficiency
High linearity
Use of switching devices
High power output
Explanation - Class‑D amplifiers sacrifice linearity for efficiency, using PWM or switching techniques.
Correct answer is: High linearity
Q.76 Which of the following statements is true regarding the Miller effect?
It increases the high‑frequency gain
It reduces the bandwidth by increasing capacitance
It is only present in MOSFETs
It eliminates noise
Explanation - The Miller effect multiplies the feedback capacitance, increasing effective input capacitance and thus reducing bandwidth.
Correct answer is: It reduces the bandwidth by increasing capacitance
Q.77 In a common‑collector (emitter follower) stage, the voltage gain is approximately:
1
β
1/β
β/(β+1)
Explanation - A common‑collector stage has a voltage gain close to unity because it mainly buffers the input signal.
Correct answer is: 1
Q.78 The term 'noise figure' is used to characterize:
The amplifier's power consumption
The amount of noise added by the amplifier
The input impedance
The output voltage swing
Explanation - Noise figure quantifies how much the amplifier degrades the signal‑to‑noise ratio.
Correct answer is: The amount of noise added by the amplifier
Q.79 Which of the following is a typical application for an instrumentation amplifier?
Amplifying audio signals
Driving motors
Reading sensor signals
Power supply regulation
Explanation - Instrumentation amplifiers are designed for precise, low‑level differential signal measurement from sensors.
Correct answer is: Reading sensor signals
Q.80 Which of the following is a key parameter of a transistor that influences its ability to operate at high frequencies?
Collector current
Early voltage
Transition frequency (f_T)
Saturation voltage
Explanation - f_T is the frequency at which the transistor's current gain drops to unity, limiting high‑frequency operation.
Correct answer is: Transition frequency (f_T)
Q.81 A feedback resistor network in a non‑inverting op‑amp amplifier sets the closed‑loop gain by:
Multiplying the open‑loop gain by the feedback factor
Dividing the input voltage by the feedback resistor
Adding a fixed voltage offset
Increasing the input impedance
Explanation - The feedback network scales the open‑loop gain to achieve the desired closed‑loop gain.
Correct answer is: Multiplying the open‑loop gain by the feedback factor
Q.82 Which component is commonly used as a source degeneration resistor in a transistor amplifier to linearize the input?
Load resistor
Emitter resistor
Collector resistor
Base resistor
Explanation - An emitter resistor provides local negative feedback, improving linearity and stability.
Correct answer is: Emitter resistor
Q.83 What is the typical purpose of a bypass capacitor across the emitter resistor in a common‑emitter amplifier?
Reduce the AC gain
Increase the AC gain
Lower the bias current
Raise the cutoff frequency
Explanation - The bypass capacitor short‑circuits the emitter resistor at AC, reducing negative feedback and increasing gain.
Correct answer is: Increase the AC gain
Q.84 Which of the following is not an advantage of a cascode amplifier?
High input impedance
High output impedance
High bandwidth
Reduced Miller effect
Explanation - A cascode amplifier actually provides a very low output impedance, not high.
Correct answer is: High output impedance
Q.85 In a BJT amplifier, the transistor's current gain (β) is defined as:
I_C / I_B
I_B / I_C
V_C / V_B
V_B / V_C
Explanation - β is the ratio of collector current to base current, indicating how many times the base current is multiplied.
Correct answer is: I_C / I_B
Q.86 A push‑pull class‑AB amplifier reduces distortion by:
Using a single transistor
Adding a large capacitor across the load
Biasing transistors slightly on in both halves of the cycle
Operating in saturation for the full cycle
Explanation - Biasing ensures smooth transition between transistors, minimizing crossover distortion.
Correct answer is: Biasing transistors slightly on in both halves of the cycle
Q.87 Which of the following is a common cause of crossover distortion in a class‑AB amplifier?
Excessive bias current
Insufficient bias current
Large load resistor
High supply voltage
Explanation - When bias is too low, transistors turn off momentarily, causing distortion at the zero crossing.
Correct answer is: Insufficient bias current
Q.88 Which of the following parameters is directly proportional to the small‑signal voltage gain of a common‑emitter amplifier?
Emitter resistance
Collector resistor
Base bias voltage
Collector‑to‑emitter voltage
Explanation - The voltage gain is approximately -g_m*R_C; increasing R_C raises the magnitude of gain.
Correct answer is: Collector resistor
Q.89 A common‑base amplifier is most suitable for which type of application?
High‑gain audio pre‑amplifier
High‑speed RF amplification
Low‑power battery operation
Precision voltage regulation
Explanation - The common‑base stage provides high frequency response and low input impedance, ideal for RF front ends.
Correct answer is: High‑speed RF amplification
Q.90 Which of the following is a primary benefit of a voltage follower (buffer) stage in analog circuits?
High voltage gain
High output impedance
Low input impedance
Isolation between circuits
Explanation - A voltage follower provides unity gain but isolates the source from the load, protecting the input stage.
Correct answer is: Isolation between circuits
Q.91 Which of the following is NOT a type of transistor used in amplifier circuits?
BJT
MOSFET
JFET
IGBT
Explanation - IGBTs are power devices used for high‑voltage DC switching, not typically used in analog amplifier signal stages.
Correct answer is: IGBT
Q.92 In a class‑A amplifier, why is the quiescent current set higher than the maximum output current?
To keep the transistor always on
To increase the bandwidth
To reduce noise
To match the load impedance
Explanation - A higher quiescent current ensures the transistor remains in its active region for the entire signal cycle.
Correct answer is: To keep the transistor always on
Q.93 Which of the following is a characteristic of a class‑D amplifier?
High distortion
Low efficiency
Switching operation
High input impedance
Explanation - Class‑D amplifiers use switching transistors to achieve high efficiency.
Correct answer is: Switching operation
Q.94 The Miller theorem is used to simplify:
The calculation of output impedance
The calculation of input capacitance with feedback
The calculation of collector current
The calculation of power dissipation
Explanation - Miller theorem transforms a feedback capacitor into an equivalent capacitance at the input node.
Correct answer is: The calculation of input capacitance with feedback
Q.95 Which of the following is an example of a negative‑feedback amplifier configuration?
Differential amplifier
Common emitter without feedback
Voltage follower
Op‑amp in a comparator mode
Explanation - The voltage follower uses negative feedback to provide unity gain with low output impedance.
Correct answer is: Voltage follower
Q.96 A transistor amplifier that uses two transistors in a push‑pull configuration to drive an AC load is called a:
Common emitter amplifier
Differential amplifier
Class‑A amplifier
Class‑B amplifier
Explanation - Class‑B uses two transistors, each conducting half the cycle, to drive the load.
Correct answer is: Class‑B amplifier
Q.97 In a common‑emitter amplifier, the emitter resistor (R_E) is often used to:
Increase voltage gain
Reduce noise
Provide local negative feedback
Increase bandwidth
Explanation - R_E introduces negative feedback that stabilizes bias and reduces distortion.
Correct answer is: Provide local negative feedback
Q.98 What is the primary disadvantage of a class‑AB amplifier compared to a class‑A amplifier?
Higher distortion at low levels
Lower efficiency
Complex biasing
Higher output impedance
Explanation - Class‑AB is less efficient than class‑A but offers lower distortion and better power handling.
Correct answer is: Lower efficiency
Q.99 Which of the following is not a typical application of an instrumentation amplifier?
Biopotential measurement
Temperature sensor output
Audio signal amplification
Differential voltage measurement
Explanation - Instrumentation amplifiers are meant for low‑level differential signals, not audio power stages.
Correct answer is: Audio signal amplification
Q.100 The 'Early voltage' of a transistor is a measure of:
High‑frequency performance
Output resistance
Temperature coefficient
Collector‑to‑emitter voltage drop
Explanation - Early voltage indicates how output resistance varies with collector current; higher V_A gives lower output resistance.
Correct answer is: Output resistance
Q.101 Which of the following components is used to provide a low‑noise, high‑input‑impedance source for an amplifier?
Voltage follower
Emitter resistor
Collector resistor
Current mirror
Explanation - A voltage follower buffers the source, presenting high impedance and low noise to the amplifier.
Correct answer is: Voltage follower
Q.102 The 'Slew rate' of an amplifier is defined as:
Maximum output voltage swing per unit time
Maximum input voltage per unit time
Maximum bandwidth
Maximum gain
Explanation - Slew rate describes how quickly the amplifier output can change in response to rapid input changes.
Correct answer is: Maximum output voltage swing per unit time
Q.103 Which of the following is an advantage of using a common‑collector (emitter follower) configuration?
High voltage gain
High input impedance
Low output impedance
High frequency response
Explanation - A common‑collector stage provides low output impedance, useful for driving subsequent stages.
Correct answer is: Low output impedance
Q.104 Which of the following is a typical characteristic of a differential amplifier?
High common‑mode rejection ratio
Low input impedance
High output impedance
High distortion
Explanation - Differential amplifiers are designed to reject signals common to both inputs, providing high CMRR.
Correct answer is: High common‑mode rejection ratio
Q.105 A BJT amplifier stage that uses a voltage divider bias network to set the base voltage is called a:
Fixed bias amplifier
Collector bias amplifier
Voltage divider bias amplifier
Self‑bias amplifier
Explanation - A voltage divider network sets the base bias voltage for stable operation.
Correct answer is: Voltage divider bias amplifier
Q.106 Which of the following is an example of a feedback type that increases the bandwidth of an amplifier?
Negative feedback
Positive feedback
Voltage‑series feedback
Current‑parallel feedback
Explanation - Negative feedback reduces gain but increases bandwidth and linearity.
Correct answer is: Negative feedback
Q.107 In a transistor amplifier, the collector current (I_C) is proportional to:
Base voltage
Emitter voltage
Base current
Collector voltage
Explanation - I_C ≈ βI_B; the collector current is proportional to base current in the active region.
Correct answer is: Base current
Q.108 What is the main purpose of a load resistor in a transistor amplifier circuit?
To set the bias point
To provide a return path for the collector current
To limit the input voltage
To stabilize the supply voltage
Explanation - The load resistor converts collector current changes into voltage variations for measurement or further amplification.
Correct answer is: To provide a return path for the collector current
Q.109 The 'bandwidth' of an amplifier is defined as:
The frequency at which the gain falls to half of the maximum
The frequency at which the gain falls to one‑third of the maximum
The maximum operating frequency
The range of input voltages
Explanation - Bandwidth is typically the -3 dB frequency point where gain drops to 0.707 of its maximum.
Correct answer is: The frequency at which the gain falls to half of the maximum
Q.110 In a differential amplifier, the common‑mode input signal is:
Amplified by the same factor as the differential signal
Attenuated by the differential gain
Common to both inputs and largely rejected
Used to bias the amplifier
Explanation - The amplifier is designed to reject common‑mode signals, allowing only the differential component to be amplified.
Correct answer is: Common to both inputs and largely rejected
Q.111 Which of the following is a key parameter in determining the noise figure of an amplifier?
Input resistance
Input noise voltage
Output impedance
Power supply voltage
Explanation - The noise figure depends on the intrinsic noise of the amplifier and its input noise voltage.
Correct answer is: Input noise voltage
Q.112 In a common‑emitter amplifier, the emitter resistor is often connected to ground through a bypass capacitor to:
Reduce the overall gain
Increase the overall gain
Lower the input impedance
Increase the output impedance
Explanation - The bypass capacitor shorts the emitter resistor for AC signals, removing local negative feedback and boosting gain.
Correct answer is: Increase the overall gain
Q.113 Which of the following is not a typical application of a power amplifier?
Driving a loudspeaker
Signal conditioning for instrumentation
Amplifying low‑level sensor output
Driving high‑power RF transmitters
Explanation - Power amplifiers provide high current/voltage swings, not low‑level signal amplification.
Correct answer is: Amplifying low‑level sensor output
Q.114 Which of the following best describes the output impedance of an op‑amp in a voltage follower configuration?
Very high
Moderate
Very low
Zero
Explanation - A voltage follower has a very low output impedance, allowing it to drive heavy loads.
Correct answer is: Very low
Q.115 A transistor amplifier that uses two transistors in a push‑pull arrangement to drive an AC load is called a:
Common emitter amplifier
Differential amplifier
Class‑A amplifier
Class‑B amplifier
Explanation - Class‑B uses two transistors, each conducting for half of the signal cycle, to drive the load efficiently.
Correct answer is: Class‑B amplifier
Q.116 Which of the following is a key advantage of a class‑D amplifier?
Low distortion
High efficiency
Simplicity
High output impedance
Explanation - Class‑D amplifiers use switching transistors, achieving efficiencies above 90%.
Correct answer is: High efficiency
Q.117 What does the term 'power factor' refer to in amplifier design?
Ratio of active to reactive power
Efficiency of the power stage
Voltage to current ratio
Load resistance
Explanation - Power factor indicates how effectively the amplifier uses AC power to produce useful DC output.
Correct answer is: Ratio of active to reactive power
Q.118 The 'common‑mode rejection ratio (CMRR)' is a measure of an amplifier's ability to reject:
Differential signals
Common‑mode signals
High‑frequency noise
Low‑frequency drift
Explanation - CMRR quantifies how much a common‑mode signal is rejected by a differential amplifier.
Correct answer is: Common‑mode signals
Q.119 Which of the following is a typical application of a voltage follower?
Amplifying audio signals
Buffering a high‑impedance source
Driving a heavy load
Generating a high‑frequency oscillator
Explanation - A voltage follower buffers a high‑impedance signal, providing low output impedance to drive subsequent stages.
Correct answer is: Buffering a high‑impedance source
Q.120 Which of the following is a typical application of a differential amplifier?
Audio pre‑amplification
Power delivery to a loudspeaker
Voltage level shifting
Differential signal measurement
Explanation - Differential amplifiers are ideal for measuring small signals with high common‑mode rejection.
Correct answer is: Differential signal measurement
Q.121 Which of the following is a typical application of a common‑collector (emitter follower) amplifier?
High‑gain pre‑amplification
Impedance matching for a low‑impedance load
Driving high‑power loads directly
Generating high‑frequency signals
Explanation - The common‑collector stage provides a low output impedance, suitable for driving low‑impedance loads.
Correct answer is: Impedance matching for a low‑impedance load
Q.122 Which of the following is a typical application of a class‑AB amplifier?
Low‑noise amplification
High‑power audio output
Digital logic buffering
High‑frequency RF amplification
Explanation - Class‑AB amplifiers are used in audio power stages to deliver moderate to high power with good linearity.
Correct answer is: High‑power audio output
Q.123 Which of the following is a typical application of a class‑C amplifier?
Audio amplification
RF power amplification
Analog signal conditioning
Low‑power logic circuits
Explanation - Class‑C amplifiers conduct for less than 180° and are used in RF power amplifiers for high efficiency.
Correct answer is: RF power amplification