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NTPC MCQs

Practice NTPC-oriented Electronics & Telecommunication Engineering MCQs with answers and explanations for technical exam preparation. Questions are arranged in pages of up to 100.

Question 205
Analog ElectronicsFrequency Response

The Miller effect in an inverting voltage amplifier effectively makes a feedback capacitance between input and output appear at the input as?

  • AA reduced capacitance only
  • BAn increased effective capacitance
  • CZero capacitance
  • DA pure inductance
Report an error
Correct Answer: B. An increased effective capacitance
Explanation: Because the output is amplified and inverted, a capacitance bridging input and output can appear as a much larger effective input capacitance.
Reference: Standard analog electronics: frequency response
Question 213
Analog ElectronicsFeedback Amplifiers

An unbypassed emitter resistor in a common-emitter amplifier primarily introduces?

  • APositive feedback
  • BEmitter degeneration or negative feedback
  • COscillation at all frequencies
  • DAvalanche breakdown
Report an error
Correct Answer: B. Emitter degeneration or negative feedback
Explanation: The emitter resistor develops degenerative negative feedback, improving stability and linearity while reducing gain.
Reference: Standard analog electronics: feedback amplifiers
Question 214
Analog ElectronicsFrequency Response

The lower cutoff frequency of an RC-coupled amplifier is mainly influenced by?

  • ACoupling and bypass capacitors
  • BTransistor breakdown voltage only
  • CPower-supply frequency only
  • DCollector color code
Report an error
Correct Answer: A. Coupling and bypass capacitors
Explanation: At low frequencies, coupling and emitter-bypass capacitor reactances become significant and reduce gain.
Reference: Standard analog electronics: frequency response
Question 215
Analog ElectronicsFrequency Response

At high frequencies, the gain of a transistor amplifier generally falls mainly because of?

  • AJunction and stray capacitances
  • BCoupling capacitors becoming open circuits only
  • CDC bias becoming exactly zero
  • DLoad resistance becoming infinite
Report an error
Correct Answer: A. Junction and stray capacitances
Explanation: Internal junction capacitances, wiring capacitance and related high-frequency effects reduce amplifier gain.
Reference: Standard analog electronics: frequency response
Question 219
Analog ElectronicsFeedback Amplifiers

In voltage-series negative feedback, the output resistance generally?

  • AIncreases
  • BDecreases
  • CBecomes infinite
  • DAlways equals input resistance
Report an error
Correct Answer: B. Decreases
Explanation: Voltage sampling with negative feedback generally lowers the closed-loop output resistance.
Reference: Standard analog electronics: feedback amplifiers
Question 221
Analog ElectronicsFeedback Amplifiers

An amplifier has A beta = 99. By what factor is its gain sensitivity to amplifier-parameter changes reduced compared with no feedback?

  • AApproximately 10
  • BApproximately 50
  • CApproximately 100
  • DApproximately 9900
Report an error
Correct Answer: C. Approximately 100
Explanation: The desensitivity factor is 1 + A beta = 100, so fractional gain variation is reduced by approximately a factor of 100.
Reference: Standard analog electronics: feedback amplifiers
Question 222
Analog ElectronicsOscillators

For a three-section RC phase-shift oscillator using identical RC sections in the usual idealized analysis, the amplifier must provide a gain magnitude of at least approximately?

  • A1
  • B3
  • C29
  • D100
Report an error
Correct Answer: C. 29
Explanation: The three-section RC network attenuates the signal; the standard idealized condition requires amplifier gain magnitude of at least about 29.
Reference: Standard analog electronics: oscillators
Question 225
Analog ElectronicsOscillators

In a Hartley oscillator, the frequency-selective tank circuit primarily uses?

  • ATwo capacitors and one resistor
  • BTwo inductive sections and a capacitor
  • COnly three resistors
  • DA crystal with no reactive components
Report an error
Correct Answer: B. Two inductive sections and a capacitor
Explanation: A Hartley oscillator uses a tapped inductor or two inductive sections with a capacitor to form its resonant tank.
Reference: Standard analog electronics: oscillators
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Question 226
Analog ElectronicsOscillators

In a Colpitts oscillator, the feedback network characteristically uses?

  • AA capacitive divider
  • BAn inductive divider only
  • CA resistive bridge only
  • DA transformer rectifier
Report an error
Correct Answer: A. A capacitive divider
Explanation: A Colpitts oscillator uses two capacitors forming a capacitive divider together with an inductor.
Reference: Standard analog electronics: oscillators
Question 227
Analog ElectronicsOscillators

A crystal oscillator is preferred when the main requirement is?

  • AVery poor frequency stability
  • BHigh frequency stability
  • CLarge DC voltage regulation
  • DLow input resistance
Report an error
Correct Answer: B. High frequency stability
Explanation: Quartz crystals have very high Q and stable resonant characteristics, giving excellent oscillator frequency stability.
Reference: Standard analog electronics: oscillators
Question 230
Analog ElectronicsDifferential Amplifiers

In an ideal BJT differential amplifier with perfectly matched transistors and equal collector resistors, applying the same signal to both inputs ideally produces a differential output of?

  • AZero
  • BEqual to twice the input
  • CInfinite
  • DEqual to the supply voltage
Report an error
Correct Answer: A. Zero
Explanation: An ideal differential amplifier rejects a signal common to both inputs, so the differential output due to a pure common-mode signal is zero.
Reference: Standard analog electronics: differential amplifiers
Question 233
Analog ElectronicsDifferential Amplifiers

The principal purpose of a constant-current source in the tail of a BJT differential pair is to?

  • AImprove bias stability and common-mode rejection
  • BMake both transistors permanently saturated
  • CReduce input resistance to zero
  • DRectify the input signal
Report an error
Correct Answer: A. Improve bias stability and common-mode rejection
Explanation: A high-resistance tail current source keeps the total emitter current nearly constant, improving differential operation and common-mode rejection.
Reference: Standard analog electronics: differential amplifiers
Question 234
Analog ElectronicsCurrent Mirrors

A basic two-transistor BJT current mirror is designed primarily to?

  • AGenerate an approximately replicated current
  • BGenerate a sine wave
  • CProvide voltage gain of exactly 100
  • DConvert AC directly to RF
Report an error
Correct Answer: A. Generate an approximately replicated current
Explanation: Matched transistors with equal base-emitter voltages can be arranged so an output collector current approximately mirrors a reference current.
Reference: Standard analog electronics: current mirrors
Question 236
Analog ElectronicsTransistor Amplifiers

The Early effect in a BJT causes collector current in the active region to?

  • ABe completely independent of VCE
  • BIncrease somewhat as VCE increases at fixed base drive
  • CBecome exactly zero
  • DReverse direction at all times
Report an error
Correct Answer: B. Increase somewhat as VCE increases at fixed base drive
Explanation: Base-width modulation causes collector current to depend slightly on collector-emitter voltage, giving a finite transistor output resistance.
Reference: Standard analog electronics: transistor amplifiers
Question 238
Analog ElectronicsPower Amplifiers

The purpose of a heat sink attached to a power transistor is primarily to?

  • AIncrease junction temperature
  • BReduce thermal resistance from the device to ambient
  • CIncrease transistor beta exactly
  • DProvide positive feedback
Report an error
Correct Answer: B. Reduce thermal resistance from the device to ambient
Explanation: A heat sink improves heat transfer away from the device, lowering junction temperature for a given power dissipation.
Reference: Standard analog electronics: power amplifiers
Question 239
Analog ElectronicsPower Amplifiers

A transistor dissipates 2 W. If the total junction-to-ambient thermal resistance is 25 degrees C/W and ambient temperature is 30 degrees C, the estimated junction temperature is?

  • A50 degrees C
  • B55 degrees C
  • C80 degrees C
  • D105 degrees C
Report an error
Correct Answer: C. 80 degrees C
Explanation: Temperature rise = P times thermal resistance = 2×25 = 50 degrees C. Junction temperature = 30+50 = 80 degrees C.
Reference: Standard analog electronics: power amplifiers
Question 240
Analog ElectronicsActive Filters

An ideal first-order low-pass active filter has a cutoff frequency of 1 kHz. At frequencies far above cutoff, its magnitude rolls off asymptotically at approximately?

  • A-10 dB/decade
  • B-20 dB/decade
  • C-40 dB/decade
  • D+20 dB/decade
Report an error
Correct Answer: B. -20 dB/decade
Explanation: Each first-order pole contributes an asymptotic attenuation slope of about -20 dB per decade beyond the cutoff region.
Reference: Standard analog electronics: active filters
Question 243
Analog ElectronicsActive Filters

A high-pass filter ideally attenuates signals primarily?

  • AAbove its cutoff frequency
  • BBelow its cutoff frequency
  • COnly exactly at resonance
  • DAt all frequencies equally
Report an error
Correct Answer: B. Below its cutoff frequency
Explanation: A high-pass filter passes frequencies above its cutoff region while attenuating lower-frequency components.
Reference: Standard analog electronics: active filters
Question 244
Analog ElectronicsActive Filters

A band-pass filter is intended primarily to?

  • APass a selected range of frequencies and attenuate frequencies outside it
  • BPass DC only
  • CReject only one exact frequency with no passband
  • DAmplify every frequency equally
Report an error
Correct Answer: A. Pass a selected range of frequencies and attenuate frequencies outside it
Explanation: A band-pass response passes frequencies between lower and upper cutoff frequencies while attenuating frequencies outside that band.
Reference: Standard analog electronics: active filters
Question 245
Analog ElectronicsComparators & Schmitt Triggers

A comparator differs from a linear op-amp amplifier mainly because a comparator is normally intended to operate?

  • AWith its output switching between high and low states
  • BOnly with exactly unity negative feedback
  • COnly as an integrator
  • DAt zero supply voltage
Report an error
Correct Answer: A. With its output switching between high and low states
Explanation: A comparator determines which input is larger and normally drives its output toward one of two limiting states rather than operating linearly.
Reference: Standard analog electronics: comparators & schmitt triggers
Question 246
Analog ElectronicsComparators & Schmitt Triggers

The hysteresis of a Schmitt trigger is defined as the difference between its?

  • AUpper and lower switching thresholds
  • BSupply voltages only
  • CInput and output resistance
  • DOpen-loop and closed-loop gain
Report an error
Correct Answer: A. Upper and lower switching thresholds
Explanation: Hysteresis is the separation between the upper threshold voltage and lower threshold voltage.
Reference: Standard analog electronics: comparators & schmitt triggers
Question 250
Analog ElectronicsOperational Amplifiers

An op-amp has an input offset voltage of 2 mV and a closed-loop noise gain of 100. Ignoring other errors, the resulting output offset magnitude is approximately?

  • A2 mV
  • B20 mV
  • C0.2 V
  • D2 V
Report an error
Correct Answer: C. 0.2 V
Explanation: Output offset due to input offset is approximately the input offset multiplied by noise gain: 2 mV × 100 = 200 mV = 0.2 V.
Reference: Standard analog electronics: operational amplifiers
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Question 253
Analog ElectronicsPower Amplifiers

A class-C amplifier has a conduction angle that is typically?

  • ALess than 180 degrees
  • BExactly 180 degrees
  • CExactly 270 degrees
  • DExactly 360 degrees
Report an error
Correct Answer: A. Less than 180 degrees
Explanation: Class-C devices conduct for less than half of each input cycle and are commonly used with tuned loads in RF applications.
Reference: Standard analog electronics: power amplifiers
Question 259
Analog ElectronicsFrequency Response

If two identical noninteracting first-order amplifier stages are cascaded, the overall response near their individual cutoff frequencies is generally?

  • AExactly identical to one stage
  • BAffected because the stage responses multiply
  • CAlways flat at all frequencies
  • DIndependent of each stage response
Report an error
Correct Answer: B. Affected because the stage responses multiply
Explanation: The overall transfer magnitude is the product of individual stage magnitudes, so cascading alters the composite cutoff behavior.
Reference: Standard analog electronics: frequency response
Question 261
Analog ElectronicsFrequency Response

In a BJT amplifier, the Miller effect associated with collector-base capacitance is especially important in which configuration?

  • ACommon-emitter voltage amplifier
  • BEmitter follower with exactly unity gain
  • CCommon-base stage with no inversion
  • DDC current mirror only
Report an error
Correct Answer: A. Common-emitter voltage amplifier
Explanation: The relatively large inverting voltage gain of a common-emitter stage can multiply the effective input capacitance caused by collector-base capacitance.
Reference: Standard analog electronics: frequency response
Question 264
Analog ElectronicsActive Filters

A second-order Butterworth low-pass filter is known for having which passband characteristic?

  • AMaximally flat magnitude response
  • BEqual ripple in the passband
  • CA notch at DC
  • DInfinite gain at cutoff
Report an error
Correct Answer: A. Maximally flat magnitude response
Explanation: The Butterworth approximation is designed for a maximally flat magnitude response in the passband.
Reference: Standard analog electronics: active filters
Question 268
Analog ElectronicsFeedback Amplifiers

Which feedback topology is commonly used to obtain a voltage amplifier with increased input resistance and reduced output resistance?

  • AVoltage-series feedback
  • BVoltage-shunt feedback
  • CCurrent-series feedback only for current output
  • DCurrent-shunt feedback
Report an error
Correct Answer: A. Voltage-series feedback
Explanation: Series mixing raises input resistance and voltage sampling lowers output resistance, which is desirable for a voltage amplifier.
Reference: Standard analog electronics: feedback amplifiers
Question 269
Analog ElectronicsOscillators

For a Wien-bridge oscillator, the lead-lag feedback network has an attenuation of approximately 1/3 at resonance, so the amplifier gain required for sustained oscillation is approximately?

  • A1
  • B2
  • C3
  • D29
Report an error
Correct Answer: C. 3
Explanation: At the balance frequency the Wien network returns about one-third of the output, so the amplifier must provide a gain of approximately 3.
Reference: Standard analog electronics: oscillators
Question 272
Analog ElectronicsOscillators

A high-Q resonant circuit is characterized by?

  • AA relatively narrow bandwidth around resonance
  • BA very broad bandwidth only
  • CZero stored energy
  • DNo frequency selectivity
Report an error
Correct Answer: A. A relatively narrow bandwidth around resonance
Explanation: For a resonator, Q is inversely related to fractional bandwidth; a higher Q means sharper resonance and narrower bandwidth.
Reference: Standard analog electronics: oscillators
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Question 276
Analog ElectronicsTransistor Amplifiers

A common-emitter stage has an unbypassed emitter resistance RE = 1 kOhm and small-signal emitter resistance re = 25 ohm. Neglecting other effects, the emitter degeneration is dominated by?

  • AThe 25 ohm intrinsic resistance only
  • BThe 1 kOhm external emitter resistor
  • CCollector-base capacitance only
  • DSupply resistance only
Report an error
Correct Answer: B. The 1 kOhm external emitter resistor
Explanation: Because RE is much larger than re, the external emitter resistance dominates the emitter degeneration and strongly reduces gain sensitivity.
Reference: Standard analog electronics: transistor amplifiers
Question 280
Network TheoryCircuit Fundamentals

According to Ohm’s law, the voltage across a resistor is equal to?

  • ACurrent divided by resistance
  • BCurrent multiplied by resistance
  • CResistance divided by current
  • DPower multiplied by current
Report an error
Correct Answer: B. Current multiplied by resistance
Explanation: Ohm's law is V = IR, where V is voltage, I is current and R is resistance.
Reference: Standard network theory: circuit fundamentals
Question 284
Network TheoryKirchhoff Laws

Kirchhoff’s Current Law states that at any node?

  • AThe algebraic sum of currents is zero
  • BThe algebraic sum of voltages is always one
  • CPower is always zero
  • DResistance is always maximum
Report an error
Correct Answer: A. The algebraic sum of currents is zero
Explanation: KCL follows conservation of charge: the algebraic sum of currents entering and leaving a node is zero.
Reference: Standard network theory: kirchhoff laws
Question 285
Network TheoryKirchhoff Laws

Kirchhoff’s Voltage Law states that around any closed loop?

  • AThe algebraic sum of currents is zero
  • BThe algebraic sum of voltages is zero
  • CAll resistances are equal
  • DAll branch currents are equal
Report an error
Correct Answer: B. The algebraic sum of voltages is zero
Explanation: KVL follows conservation of energy: the algebraic sum of voltage rises and drops around a closed loop is zero.
Reference: Standard network theory: kirchhoff laws
Question 291
Network TheoryNetwork Theorems

The superposition theorem is directly applicable to which type of network?

  • ALinear networks
  • BOnly nonlinear networks
  • COnly magnetic circuits
  • DOnly circuits with one source
Report an error
Correct Answer: A. Linear networks
Explanation: Superposition applies to linear circuits containing multiple independent sources; responses from individual sources are summed.
Reference: Standard network theory: network theorems
Question 292
Network TheoryNetwork Theorems

Thevenin’s theorem replaces a linear two-terminal network by?

  • AA current source in series with resistance
  • BA voltage source in series with resistance
  • CA voltage source in parallel with zero resistance only
  • DA capacitor and inductor only
Report an error
Correct Answer: B. A voltage source in series with resistance
Explanation: The Thevenin equivalent consists of an ideal voltage source Vth in series with an equivalent resistance or impedance.
Reference: Standard network theory: network theorems
Question 293
Network TheoryNetwork Theorems

Norton’s theorem replaces a linear two-terminal network by?

  • AA current source in parallel with resistance
  • BA voltage source in series with resistance
  • COnly a resistance
  • DOnly an inductor
Report an error
Correct Answer: A. A current source in parallel with resistance
Explanation: The Norton equivalent consists of an ideal current source IN in parallel with an equivalent resistance or impedance.
Reference: Standard network theory: network theorems
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