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All Electronics & Telecommunication MCQs

Browse Electronics & Telecommunication Engineering MCQs with four options, hidden answers, concise explanations and references where available. Questions are organized in pages of up to 100 for focused practice.

Question 1401
Digital ElectronicsMemory

A FIFO memory is best described by which ordering rule?

  • AFirst data written is the first data read
  • BLast data written is always the first data read
  • CData is read in random analog order
  • DOnly zero values can be stored
Report an error
Correct Answer: A. First data written is the first data read
Explanation: FIFO means First-In, First-Out: entries leave the buffer in the same order in which they entered.
Reference: Standard digital electronics: FIFO
Question 1402
Digital ElectronicsMemory

Which pair of pointer conditions is commonly used in a FIFO to determine whether reads or writes should be blocked?

  • AEmpty and full
  • BCarry and borrow only
  • CSet and reset only
  • DGain and phase
Report an error
Correct Answer: A. Empty and full
Explanation: FIFO control logic tracks read and write positions and derives EMPTY and FULL conditions to prevent invalid reads and overwriting of unread data.
Reference: Standard digital electronics: FIFO status
Question 1403
Digital ElectronicsADC & DAC

A dual-slope ADC is particularly valued in digital measurement instruments because its integrating operation provides good rejection of?

  • ACertain periodic noise such as mains-frequency interference
  • BAll possible quantization error
  • CEvery clock error regardless of frequency
  • DMemory leakage
Report an error
Correct Answer: A. Certain periodic noise such as mains-frequency interference
Explanation: Dual-slope conversion integrates the input over a defined interval; choosing the interval appropriately can strongly reject periodic interference such as 50/60 Hz mains noise.
Reference: Standard digital electronics: dual-slope ADC
Question 1404
Digital ElectronicsADC & DAC

In an ADC, differential nonlinearity (DNL) describes deviation of?

  • AAn individual code-bin width from the ideal 1-LSB step
  • BThe supply voltage from zero
  • CThe clock duty cycle from 100 percent
  • DThe number of output bits from an integer
Report an error
Correct Answer: A. An individual code-bin width from the ideal 1-LSB step
Explanation: DNL measures how much each actual transition step or code-bin width differs from the ideal one-LSB size.
Reference: Standard digital electronics: ADC differential nonlinearity
Question 1405
Digital ElectronicsADC & DAC

An ADC is said to have a missing code when?

  • AAt least one digital output code is never produced for any input within the conversion range
  • BEvery code occurs twice
  • CThe input is exactly zero
  • DThe ADC has no clock pin
Report an error
Correct Answer: A. At least one digital output code is never produced for any input within the conversion range
Explanation: A missing code is an output value that the converter skips entirely as the analog input is swept through its range, often associated with excessive DNL.
Reference: Standard digital electronics: ADC missing codes
Question 1406
Digital ElectronicsADC & DAC

For an ideal monotonic DAC, increasing the digital input code by one count should?

  • ANever cause the analog output to move in the opposite direction
  • BAlways force the output to zero
  • CReverse the output polarity every step
  • DProduce exactly two output transitions
Report an error
Correct Answer: A. Never cause the analog output to move in the opposite direction
Explanation: Monotonicity means the analog output never reverses direction when the input code changes monotonically in one direction.
Reference: Standard digital electronics: DAC monotonicity
Question 1407
Digital ElectronicsADC & DAC

A DAC has a settling time specification of 2 microseconds. This specification primarily indicates the time required after an input-code change for the analog output to?

  • AEnter and remain within a specified error band around its final value
  • BBegin oscillating indefinitely
  • CBecome a digital code
  • DErase the input register
Report an error
Correct Answer: A. Enter and remain within a specified error band around its final value
Explanation: Settling time is measured from a code transition until the analog output reaches and stays within a specified tolerance around its final value.
Reference: Standard digital electronics: DAC settling time
Question 1410
Electronic Devices & CircuitsSemiconductor Fundamentals

Carrier drift current in a semiconductor is produced primarily by?

  • AAn applied electric field
  • BA carrier concentration gradient only
  • COptical reflection only
  • DA magnetic field with no electric field
Report an error
Correct Answer: A. An applied electric field
Explanation: Drift is the directed motion of charge carriers caused by an applied electric field.
Reference: Standard semiconductor electronics: drift current
Question 1411
Electronic Devices & CircuitsSemiconductor Fundamentals

Carrier diffusion current arises primarily because of?

  • AA spatial carrier-concentration gradient
  • BA perfectly uniform carrier concentration
  • CZero temperature only
  • DAn ideal short circuit
Report an error
Correct Answer: A. A spatial carrier-concentration gradient
Explanation: Diffusion results from random carrier motion combined with a concentration gradient, producing net transport from higher to lower concentration.
Reference: Standard semiconductor electronics: diffusion current
Question 1414
Electronic Devices & CircuitsPN Junction Diode

The small-signal resistance of a forward-biased diode at a fixed operating point is approximately proportional to?

  • AThermal voltage divided by diode current
  • BDiode current divided by thermal voltage
  • CSquare of reverse voltage only
  • DZero for every current
Report an error
Correct Answer: A. Thermal voltage divided by diode current
Explanation: From the exponential diode equation, the incremental resistance is approximately rd = nVT/ID at the operating point.
Reference: Standard semiconductor electronics: diode small-signal resistance
Question 1416
Electronic Devices & CircuitsPN Junction Diode

The junction capacitance of a reverse-biased PN diode generally does what as reverse-bias magnitude increases?

  • ADecreases
  • BIncreases without limit
  • CRemains exactly constant
  • DBecomes negative
Report an error
Correct Answer: A. Decreases
Explanation: Increasing reverse bias widens the depletion region. Since junction capacitance is inversely related to depletion width, the capacitance decreases.
Reference: Standard semiconductor electronics: transition capacitance
Question 1417
Electronic Devices & CircuitsSpecial Diodes

A varactor diode is primarily used as a voltage-controlled?

  • ACapacitance
  • BCurrent source
  • CInductance heater
  • DOptical amplifier
Report an error
Correct Answer: A. Capacitance
Explanation: A reverse-biased varactor exploits the voltage dependence of PN-junction capacitance, making it useful for electronic tuning.
Reference: Standard electronics: varactor diode
Question 1418
Electronic Devices & CircuitsPN Junction Diode

Avalanche breakdown in a PN junction is mainly associated with?

  • AImpact ionization and carrier multiplication
  • BForward-bias recombination only
  • CMechanical contact bounce
  • DZero electric field
Report an error
Correct Answer: A. Impact ionization and carrier multiplication
Explanation: In avalanche breakdown, carriers accelerated by a strong electric field create additional electron-hole pairs through impact ionization.
Reference: Standard semiconductor electronics: avalanche breakdown
Question 1419
Electronic Devices & CircuitsPN Junction Diode

Compared with avalanche breakdown, Zener breakdown is most strongly associated with?

  • AQuantum-mechanical tunneling in a heavily doped junction
  • BImpact ionization in a lightly doped junction only
  • CThermal radiation from an LED
  • DTransistor saturation
Report an error
Correct Answer: A. Quantum-mechanical tunneling in a heavily doped junction
Explanation: Zener breakdown occurs in heavily doped junctions with narrow depletion regions, where a strong field enables tunneling.
Reference: Standard semiconductor electronics: Zener breakdown mechanism
Question 1426
Electronic Devices & CircuitsBJT

The Early effect in a BJT refers primarily to variation of collector current with collector-emitter voltage due to?

  • ABase-width modulation
  • BGate-oxide tunneling
  • CZener regulation
  • DEmitter resistance only
Report an error
Correct Answer: A. Base-width modulation
Explanation: Increasing collector-base reverse bias widens the depletion region into the base, reducing effective base width and changing collector current; this is the Early effect.
Reference: Standard transistor electronics: Early effect
Question 1430
Electronic Devices & CircuitsFET & MOSFET

In a MOSFET, channel-length modulation in saturation causes the drain current to?

  • AIncrease slightly as VDS increases
  • BRemain exactly independent of VDS in every real device
  • CFall exactly to zero
  • DReverse direction automatically
Report an error
Correct Answer: A. Increase slightly as VDS increases
Explanation: Channel-length modulation shortens the effective channel as VDS rises, giving the saturation-region output characteristic a finite positive slope.
Reference: Standard electronics: MOSFET channel-length modulation
Question 1431
Electronic Devices & CircuitsFET & MOSFET

The body effect in an NMOS transistor generally causes threshold voltage magnitude to do what when source-to-body reverse bias increases?

  • AIncrease
  • BDecrease to zero
  • CRemain exactly unchanged
  • DBecome an AC frequency
Report an error
Correct Answer: A. Increase
Explanation: Increasing source-body reverse bias increases the threshold voltage required to form the inversion channel; this is the MOSFET body effect.
Reference: Standard electronics: MOSFET body effect
Question 1432
Electronic Devices & CircuitsAmplifier Frequency Response

A cascode amplifier is commonly used because it can provide high gain while reducing the influence of which high-frequency effect associated with input-output capacitance?

  • AMiller effect
  • BHall effect
  • CZener effect
  • DPhotoelectric effect
Report an error
Correct Answer: A. Miller effect
Explanation: The cascode keeps the voltage variation across the input transistor's feedback capacitance relatively small, reducing Miller multiplication and improving high-frequency response.
Reference: Standard analog electronics: cascode and Miller effect
Question 1433
Electronic Devices & CircuitsPN Junction Diode

A silicon PN junction has a reverse saturation current of 10 nA. Using the ideal diode equation with n=1 and VT=25 mV, approximately by what factor does the forward current increase when the forward voltage rises by 50 mV in the exponential region?

  • A2
  • B4
  • C7.4
  • D100
Report an error
Correct Answer: C. 7.4
Explanation: The current ratio is exp(ΔV/VT)=exp(50/25)=e^2≈7.4, assuming the exponential term dominates.
Reference: Standard semiconductor electronics: diode exponential characteristic
Question 1434
Electronic Devices & CircuitsPN Junction Diode

Reverse recovery time of a PN diode is mainly associated with?

  • ARemoval of stored charge when switching from forward conduction to reverse blocking
  • BTime required to heat the package
  • CForward voltage becoming exactly zero
  • DZener voltage regulation only
Report an error
Correct Answer: A. Removal of stored charge when switching from forward conduction to reverse blocking
Explanation: After forward conduction, stored minority-carrier charge must be removed before the diode fully blocks reverse current, producing reverse recovery time.
Reference: Standard semiconductor electronics: diode reverse recovery
Question 1435
Electronic Devices & CircuitsSpecial Diodes

A Schottky diode generally switches faster than an ordinary PN diode mainly because it is primarily a?

  • AMajority-carrier device with little minority-carrier charge storage
  • BDevice with an extremely thick depletion region only
  • CLight-emitting junction
  • DCurrent-controlled transistor
Report an error
Correct Answer: A. Majority-carrier device with little minority-carrier charge storage
Explanation: Schottky conduction mainly involves majority carriers, so there is little minority-carrier storage and reverse-recovery delay is small.
Reference: Standard electronics: Schottky diode
Question 1436
Electronic Devices & CircuitsSpecial Diodes

A PIN diode contains which structure between its heavily doped P and N regions?

  • AA relatively wide intrinsic region
  • BA metallic collector
  • CA second gate oxide
  • DA permanent short circuit
Report an error
Correct Answer: A. A relatively wide intrinsic region
Explanation: A PIN diode has a P-I-N structure. The intrinsic region gives useful RF switching, attenuation, and photodetection characteristics.
Reference: Standard electronics: PIN diode
Question 1437
Electronic Devices & CircuitsSpecial Diodes

At radio frequencies, a forward-biased PIN diode is often used approximately as a?

  • ACurrent-controlled RF resistance
  • BZener reference only
  • CLight source only
  • DNegative capacitor only
Report an error
Correct Answer: A. Current-controlled RF resistance
Explanation: Stored charge in the intrinsic region makes a forward-biased PIN diode behave approximately as a controllable low RF resistance, useful in RF switches and attenuators.
Reference: Standard electronics: PIN diode RF application
Question 1438
Electronic Devices & CircuitsSpecial Diodes

A tunnel diode exhibits a region of negative differential resistance because of?

  • AQuantum-mechanical tunneling in a very heavily doped junction
  • BOrdinary transformer action
  • CMechanical vibration
  • DAvalanche multiplication only
Report an error
Correct Answer: A. Quantum-mechanical tunneling in a very heavily doped junction
Explanation: Heavy doping creates a very narrow junction that permits quantum tunneling. Over part of its characteristic, current decreases as voltage increases, producing negative differential resistance.
Reference: Standard electronics: tunnel diode
Question 1439
Electronic Devices & CircuitsOptoelectronic Devices

A solar cell converts incident optical energy directly into electrical energy primarily through the?

  • APhotovoltaic effect
  • BZener effect
  • CMiller effect
  • DEarly effect
Report an error
Correct Answer: A. Photovoltaic effect
Explanation: Light-generated electron-hole pairs separated by the built-in junction field produce a voltage and current, which is the photovoltaic effect.
Reference: Standard optoelectronics: solar cell
Question 1440
Electronic Devices & CircuitsOptoelectronic Devices

An optocoupler is primarily used when a circuit requires?

  • AElectrical isolation while transferring a signal optically
  • BLarge DC power amplification without isolation
  • CFrequency division only
  • DMechanical switching only
Report an error
Correct Answer: A. Electrical isolation while transferring a signal optically
Explanation: An optocoupler uses a light emitter and photosensitive receiver to transfer information across an electrically isolated barrier.
Reference: Standard optoelectronics: optocoupler
Question 1441
Electronic Devices & CircuitsOptoelectronic Devices

In a phototransistor, incident light primarily acts like?

  • AA base-drive mechanism that controls collector current
  • BA collector resistor
  • CA gate oxide
  • DAn emitter bypass capacitor
Report an error
Correct Answer: A. A base-drive mechanism that controls collector current
Explanation: Photogenerated carriers provide an effective base drive, and transistor action amplifies the resulting photocurrent.
Reference: Standard optoelectronics: phototransistor
Question 1442
Electronic Devices & CircuitsAmplifier Frequency Response

For a BJT amplifier, the Miller effect can make a feedback capacitance between collector and base appear at the input as?

  • AA larger effective capacitance
  • BExactly zero capacitance
  • CA pure inductance
  • DA negative resistance only
Report an error
Correct Answer: A. A larger effective capacitance
Explanation: Voltage gain across a feedback capacitance can multiply its apparent input effect, increasing effective input capacitance and reducing high-frequency bandwidth.
Reference: Standard analog electronics: Miller effect
Question 1443
Electronic Devices & CircuitsAmplifier Frequency Response

The dominant low-frequency cutoff of a capacitively coupled transistor amplifier is commonly influenced by?

  • ACoupling and bypass capacitors with the resistances they see
  • BTransistor transit time only
  • CJunction breakdown voltage only
  • DCollector power rating only
Report an error
Correct Answer: A. Coupling and bypass capacitors with the resistances they see
Explanation: At low frequencies, coupling and emitter/source bypass capacitors have larger reactance, creating high-pass poles that determine the low-frequency response.
Reference: Standard analog electronics: low-frequency response
Question 1445
Electronic Devices & CircuitsFeedback Amplifiers

For a voltage-series negative-feedback amplifier, applying negative feedback generally causes input resistance to?

  • AIncrease
  • BDecrease to zero
  • CRemain exactly unchanged in all cases
  • DBecome negative
Report an error
Correct Answer: A. Increase
Explanation: Series mixing at the input tends to increase the input resistance of a voltage-series feedback amplifier.
Reference: Standard analog electronics: feedback and input resistance
Question 1446
Electronic Devices & CircuitsFeedback Amplifiers

For a voltage-series negative-feedback amplifier, output resistance generally?

  • ADecreases
  • BIncreases without limit
  • CBecomes exactly equal to input resistance
  • DIs independent of feedback in every circuit
Report an error
Correct Answer: A. Decreases
Explanation: Voltage sampling with negative feedback tends to reduce output resistance, improving voltage-source behavior.
Reference: Standard analog electronics: feedback and output resistance
Question 1448
Electronic Devices & CircuitsFeedback Amplifiers

The sensitivity of closed-loop gain to variations in open-loop gain is reduced by approximately which factor in a negative-feedback amplifier?

  • A1+A beta
  • BA-beta
  • C1-A beta
  • DA/beta only
Report an error
Correct Answer: A. 1+A beta
Explanation: Negative feedback desensitizes the gain; fractional gain variation is reduced approximately by the desensitivity factor 1+Aβ.
Reference: Standard analog electronics: feedback desensitivity
Question 1449
Electronic Devices & CircuitsOscillators

For sustained sinusoidal oscillation, the Barkhausen criterion requires the magnitude of loop gain to be approximately unity and total loop phase shift to be?

  • A0 degrees or an integer multiple of 360 degrees
  • B90 degrees only
  • C180 degrees only regardless of inversion
  • D45 degrees only
Report an error
Correct Answer: A. 0 degrees or an integer multiple of 360 degrees
Explanation: At the oscillation frequency, positive regenerative feedback requires |Aβ|≈1 and net loop phase 0° modulo 360°.
Reference: Standard analog electronics: Barkhausen criterion
Question 1450
Electronic Devices & CircuitsOscillators

A Wien-bridge oscillator is especially suitable for generating?

  • ALow-distortion sinusoidal signals over audio and moderate frequencies
  • BDC only
  • CRandom digital pulses only
  • DMicrowave power without resonators
Report an error
Correct Answer: A. Low-distortion sinusoidal signals over audio and moderate frequencies
Explanation: The Wien bridge provides frequency-selective positive feedback and is widely used for low-distortion sine-wave generation.
Reference: Standard analog electronics: Wien-bridge oscillator
Question 1452
Electronic Devices & CircuitsOscillators

A crystal oscillator achieves high frequency stability mainly because a quartz crystal has a very high?

  • AQuality factor Q
  • BForward current gain beta
  • CJunction capacitance only
  • DSlew rate
Report an error
Correct Answer: A. Quality factor Q
Explanation: Quartz resonators have very high Q, producing a narrow and stable resonance that gives excellent oscillator frequency stability.
Reference: Standard analog electronics: crystal oscillator
Question 1453
Electronic Devices & CircuitsDifferential Amplifiers

In an ideal differential amplifier, common-mode gain should be?

  • AZero
  • BUnity
  • CInfinite
  • DEqual to differential gain
Report an error
Correct Answer: A. Zero
Explanation: An ideal differential amplifier responds only to the difference between its inputs and rejects signals common to both, so ideal common-mode gain is zero.
Reference: Standard analog electronics: differential amplifier
Question 1456
Electronic Devices & CircuitsDifferential Amplifiers

In a BJT differential pair with an ideal constant tail-current source, increasing the differential input toward one transistor tends to?

  • ASteer more of the fixed tail current into that transistor
  • BIncrease both collector currents equally without limit
  • CForce both transistors permanently off
  • DEliminate the tail current
Report an error
Correct Answer: A. Steer more of the fixed tail current into that transistor
Explanation: A differential pair steers an approximately fixed tail current between its two devices according to the differential input voltage.
Reference: Standard analog electronics: differential pair current steering
Question 1457
Electronic Devices & CircuitsCurrent Mirrors

A current mirror is commonly used in integrated analog circuits primarily to?

  • AReplicate or establish bias currents
  • BGenerate optical isolation
  • CPerform rectification only
  • DStore digital data permanently
Report an error
Correct Answer: A. Replicate or establish bias currents
Explanation: Matched transistors arranged as a current mirror provide approximately replicated reference currents and are widely used for IC biasing and active loads.
Reference: Standard analog electronics: current mirror
Question 1458
Electronic Devices & CircuitsCurrent Mirrors

In an ideal BJT current mirror using matched transistors, the reference current is 2 mA. Neglecting base currents and mismatch, the mirrored output current is approximately?

  • A0.2 mA
  • B1 mA
  • C2 mA
  • D20 mA
Report an error
Correct Answer: C. 2 mA
Explanation: For matched transistors with equal base-emitter voltage, the ideal mirror reproduces the reference current, so the output is approximately 2 mA.
Reference: Standard analog electronics: ideal BJT current mirror
Question 1459
Electronic Devices & CircuitsCurrent Mirrors

The principal advantage of a Widlar current source over a simple current mirror is its ability to generate?

  • AA relatively small output current without requiring an extremely large resistor
  • BAn AC voltage with zero DC bias
  • CInfinite current gain
  • DA digital clock signal
Report an error
Correct Answer: A. A relatively small output current without requiring an extremely large resistor
Explanation: Emitter degeneration in one mirror transistor allows the Widlar circuit to produce small bias currents using practical resistor values.
Reference: Standard analog electronics: Widlar current source
Question 1460
Electronic Devices & CircuitsCurrent Mirrors

Compared with a simple current mirror, a cascode current mirror is mainly used to obtain?

  • AHigher output resistance and better current-source behavior
  • BLower input resistance only
  • CZero supply voltage
  • DA square-wave output
Report an error
Correct Answer: A. Higher output resistance and better current-source behavior
Explanation: The cascode arrangement reduces the effect of output-voltage variation on mirrored current, substantially increasing output resistance.
Reference: Standard analog electronics: cascode current mirror
Question 1461
Electronic Devices & CircuitsDifferential Amplifiers

In a differential amplifier, using a high-output-resistance tail current source generally improves?

  • ACommon-mode rejection
  • BRectifier efficiency
  • CDiode reverse recovery
  • DLED optical power only
Report an error
Correct Answer: A. Common-mode rejection
Explanation: A high-resistance tail source makes the total tail current less sensitive to common-mode input changes, thereby improving CMRR.
Reference: Standard analog electronics: differential pair tail source
Question 1462
Electronic Devices & CircuitsDifferential Amplifiers

For a perfectly balanced BJT differential pair with zero differential input and an ideal tail current of 2 mA, each transistor carries approximately?

  • A0 mA
  • B0.5 mA
  • C1 mA
  • D2 mA
Report an error
Correct Answer: C. 1 mA
Explanation: With matched devices and equal input voltages, the ideal 2 mA tail current divides equally, giving approximately 1 mA in each transistor.
Reference: Standard analog electronics: differential pair bias
Question 1463
Electronic Devices & CircuitsDifferential Amplifiers

An active load is often used in an integrated differential amplifier primarily because it can provide?

  • AHigh effective load resistance and increased voltage gain
  • BMechanical isolation
  • CA low-frequency clock
  • DA fixed diode forward drop only
Report an error
Correct Answer: A. High effective load resistance and increased voltage gain
Explanation: Transistor active loads can present a high small-signal resistance while occupying little IC area, which increases amplifier voltage gain.
Reference: Standard analog electronics: active loads
Question 1465
Electronic Devices & CircuitsOperational Amplifiers

An ideal op-amp comparator with no feedback receives V+ = 0.2 V and V- = 0.1 V. Its output tends toward?

  • AThe positive saturation level
  • BThe negative saturation level
  • CExactly zero in all cases
  • DA sinusoid at the input frequency
Report an error
Correct Answer: A. The positive saturation level
Explanation: Because V+ exceeds V-, the large open-loop gain drives the output toward the positive saturation rail.
Reference: Standard analog electronics: op-amp comparator
Question 1466
Electronic Devices & CircuitsOperational Amplifiers

A Schmitt-trigger comparator intentionally uses positive feedback mainly to introduce?

  • AHysteresis with two switching thresholds
  • BInfinite input current
  • CA fixed 180-degree phase shift at all frequencies
  • DFull-wave rectification
Report an error
Correct Answer: A. Hysteresis with two switching thresholds
Explanation: Positive feedback creates separate upper and lower switching thresholds, improving noise immunity around the transition level.
Reference: Standard analog electronics: Schmitt trigger
Question 1467
Electronic Devices & CircuitsOperational Amplifiers

An op-amp has a gain-bandwidth product of 1 MHz. For a closed-loop noise gain of 100 in a single-pole approximation, the expected bandwidth is approximately?

  • A1 kHz
  • B10 kHz
  • C100 kHz
  • D1 MHz
Report an error
Correct Answer: B. 10 kHz
Explanation: For a single-pole compensated op-amp, closed-loop bandwidth is approximately GBW divided by noise gain: 1 MHz/100 = 10 kHz.
Reference: Standard analog electronics: gain-bandwidth product
Question 1468
Electronic Devices & CircuitsOperational Amplifiers

An op-amp has an input offset voltage of 2 mV and is used with a closed-loop noise gain of 50. Ignoring other errors, the output offset contribution is approximately?

  • A0.04 mV
  • B2 mV
  • C100 mV
  • D2 V
Report an error
Correct Answer: C. 100 mV
Explanation: The input-referred offset is amplified by the circuit's noise gain, giving about 2 mV × 50 = 100 mV.
Reference: Standard analog electronics: input offset voltage
Question 1469
Electronic Devices & CircuitsOperational Amplifiers

Input bias current in a practical bipolar-input op-amp refers approximately to?

  • AThe average DC currents entering or leaving the two input terminals
  • BThe maximum output load current
  • CThe current through the power-supply fuse
  • DThe feedback current only
Report an error
Correct Answer: A. The average DC currents entering or leaving the two input terminals
Explanation: Practical input transistors require small DC bias currents. Input bias current is commonly defined as the average magnitude of the two input currents.
Reference: Standard analog electronics: input bias current
Question 1470
Electronic Devices & CircuitsOperational Amplifiers

Input offset current of an op-amp is commonly defined as the?

  • ADifference between the two input bias currents
  • BSum of supply currents
  • CMaximum output current
  • DCurrent through the feedback capacitor only
Report an error
Correct Answer: A. Difference between the two input bias currents
Explanation: Input offset current quantifies mismatch between the two input bias currents and is commonly specified as their difference in magnitude.
Reference: Standard analog electronics: input offset current
Question 1471
Electronic Devices & CircuitsOperational Amplifiers

A practical op-amp has a slew rate of 0.5 V/microsecond. What is the largest sine-wave peak amplitude that can be reproduced at 10 kHz without slew-rate limiting, using SR = 2*pi*f*Vp?

  • AAbout 0.8 V
  • BAbout 8 V
  • CAbout 80 V
  • DAbout 800 V
Report an error
Correct Answer: B. About 8 V
Explanation: Vp = SR/(2πf) = 0.5×10^6/(2π×10^4) ≈ 7.96 V, so about 8 V.
Reference: Standard analog electronics: slew-rate calculation
Question 1472
Electronic Devices & CircuitsInstrumentation Amplifiers

In an ideal instrumentation amplifier, a key desired characteristic is?

  • AHigh input impedance with high common-mode rejection
  • BVery low input impedance at both inputs
  • CNo differential gain
  • DOperation only as an oscillator
Report an error
Correct Answer: A. High input impedance with high common-mode rejection
Explanation: Instrumentation amplifiers are designed to amplify small differential signals while loading sources minimally and rejecting large common-mode components.
Reference: Standard analog electronics: instrumentation amplifier
Question 1473
Electronic Devices & CircuitsInstrumentation Amplifiers

A three-op-amp instrumentation amplifier is widely used with bridge sensors because it can amplify?

  • AA small differential signal riding on a common-mode voltage
  • BOnly a pure DC supply voltage
  • COnly digital logic levels
  • DOnly oscillator noise
Report an error
Correct Answer: A. A small differential signal riding on a common-mode voltage
Explanation: Bridge sensors often produce a small differential output superimposed on a common-mode level; an instrumentation amplifier provides gain with strong common-mode rejection.
Reference: Standard analog electronics: bridge sensor interface
Question 1474
Electronic Devices & CircuitsPower Amplifiers

In a class-B complementary push-pull output stage, crossover distortion occurs mainly near?

  • AThe zero crossing where both transistors may be insufficiently conducting
  • BThe positive supply rail only
  • CThe maximum power point only
  • DThe transistor breakdown voltage only
Report an error
Correct Answer: A. The zero crossing where both transistors may be insufficiently conducting
Explanation: Near zero input, neither transistor may conduct until its base-emitter threshold is reached, producing a dead zone and crossover distortion.
Reference: Standard analog electronics: class-B crossover distortion
Question 1475
Electronic Devices & CircuitsPower Amplifiers

Biasing a complementary push-pull output stage slightly into conduction changes class B toward class AB mainly to?

  • AReduce crossover distortion
  • BEliminate all power dissipation
  • CForce both devices permanently into cutoff
  • DCreate negative resistance
Report an error
Correct Answer: A. Reduce crossover distortion
Explanation: Class-AB bias keeps both output devices slightly conducting around zero crossing, reducing the dead zone responsible for crossover distortion.
Reference: Standard analog electronics: class-AB operation
Question 1478
Electronic Devices & CircuitsPower Amplifiers

A class-C amplifier conducts for a portion of the input cycle that is typically?

  • AGreater than 360 degrees
  • BExactly 360 degrees
  • CLess than 180 degrees
  • DExactly 180 degrees
Report an error
Correct Answer: C. Less than 180 degrees
Explanation: Class-C bias allows device current for less than half of each cycle. Tuned circuits are commonly used to recover a sinusoidal output in RF applications.
Reference: Standard analog electronics: class-C operation
Question 1479
Electronic Devices & CircuitsBJT Biasing

Thermal runaway in a BJT bias circuit is associated with a self-reinforcing rise in collector current caused by?

  • ATemperature-dependent device changes and increased power dissipation
  • BA decrease in temperature to absolute zero
  • CAn ideal current source with infinite compliance
  • DA disconnected power supply
Report an error
Correct Answer: A. Temperature-dependent device changes and increased power dissipation
Explanation: Higher junction temperature can increase leakage and alter VBE-related current, increasing dissipation and temperature further unless bias stabilization limits the process.
Reference: Standard transistor electronics: thermal runaway
Question 1480
Electronic Devices & CircuitsBJT Biasing

Emitter resistance in a BJT bias circuit improves thermal stability mainly by providing?

  • ANegative feedback against increases in emitter and collector current
  • BPositive feedback that increases current indefinitely
  • COptical isolation
  • DA higher transistor breakdown voltage directly
Report an error
Correct Answer: A. Negative feedback against increases in emitter and collector current
Explanation: If current rises, the emitter voltage rises across RE, reducing effective base-emitter drive and opposing the current increase.
Reference: Standard transistor electronics: emitter degeneration and bias stability
Question 1481
Electronic Devices & CircuitsThermal Design

A heat sink attached to a power transistor primarily reduces the thermal resistance from the device toward ambient so that?

  • AJunction temperature can be kept lower for a given power dissipation
  • BCurrent gain becomes infinite
  • CBase current becomes exactly zero
  • DThe transistor becomes a photodiode
Report an error
Correct Answer: A. Junction temperature can be kept lower for a given power dissipation
Explanation: A heat sink improves heat transfer away from the device, lowering junction temperature for a specified dissipated power and ambient condition.
Reference: Standard electronics: transistor heat sinking
Question 1482
Electronic Devices & CircuitsThermal Design

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

  • A55 degrees C
  • B60 degrees C
  • C85 degrees C
  • D115 degrees C
Report an error
Correct Answer: C. 85 degrees C
Explanation: Temperature rise is P×theta = 2×30 = 60 degrees C. Adding 25 degrees C ambient gives an estimated junction temperature of 85 degrees C.
Reference: Standard electronics: thermal resistance calculation
Question 1483
Electronic Devices & CircuitsSemiconductor Fundamentals

For a semiconductor, conductivity sigma is approximately q(n mu_n + p mu_p). If electron concentration increases while mobilities and hole concentration remain unchanged, conductivity generally?

  • AIncreases
  • BDecreases
  • CBecomes zero
  • DRemains exactly unchanged
Report an error
Correct Answer: A. Increases
Explanation: The electron term q n mu_n increases with electron concentration, so total conductivity increases under the stated assumptions.
Reference: Standard semiconductor electronics: conductivity
Question 1484
Electronic Devices & CircuitsSemiconductor Fundamentals

The resistivity of a homogeneous semiconductor is the reciprocal of its?

  • AConductivity
  • BMobility only
  • CCarrier lifetime
  • DBand gap only
Report an error
Correct Answer: A. Conductivity
Explanation: Electrical resistivity rho and conductivity sigma are related by rho=1/sigma.
Reference: Standard semiconductor electronics: resistivity and conductivity
Question 1487
Electronic Devices & CircuitsSemiconductor Fundamentals

Minority-carrier diffusion length L is related to diffusion coefficient D and carrier lifetime tau by?

  • AL=sqrt(D tau)
  • BL=D/tau
  • CL=D tau
  • DL=sqrt(D/tau)
Report an error
Correct Answer: A. L=sqrt(D tau)
Explanation: The characteristic diffusion length is L=sqrt(D tau), describing the average scale over which excess minority carriers diffuse before recombination.
Reference: Standard semiconductor electronics: diffusion length
Question 1488
Electronic Devices & CircuitsSemiconductor Fundamentals

In an n-type semiconductor at equilibrium, moving the Fermi level closer to the conduction band generally indicates?

  • AHigher electron concentration
  • BHigher hole concentration only
  • CZero carrier concentration
  • DAn insulating state necessarily
Report an error
Correct Answer: A. Higher electron concentration
Explanation: For nondegenerate n-type material, a Fermi level closer to the conduction band corresponds to a larger equilibrium electron concentration.
Reference: Standard semiconductor electronics: Fermi level
Question 1489
Electronic Devices & CircuitsSemiconductor Devices

A metal-semiconductor contact designed to behave approximately as a non-rectifying low-resistance connection is called an?

  • AOhmic contact
  • BAvalanche junction
  • CTunnel barrier oscillator
  • DPhotovoltaic junction
Report an error
Correct Answer: A. Ohmic contact
Explanation: An ohmic contact is engineered so current can flow readily in both directions with approximately linear current-voltage behavior over its intended range.
Reference: Standard semiconductor electronics: ohmic contact
Question 1490
Electronic Devices & CircuitsSpecial Diodes

A Schottky barrier junction is formed primarily between?

  • AA metal and a semiconductor
  • BTwo identical metal wires
  • CTwo insulating layers only
  • DA BJT collector and emitter short
Report an error
Correct Answer: A. A metal and a semiconductor
Explanation: A Schottky diode uses a rectifying metal-semiconductor junction rather than a conventional PN junction.
Reference: Standard semiconductor electronics: Schottky barrier
Question 1491
Electronic Devices & CircuitsSpecial Diodes

The forward voltage of a silicon Schottky diode at ordinary current levels is commonly lower than that of a silicon PN diode mainly because of its?

  • AMetal-semiconductor majority-carrier conduction mechanism
  • BMuch larger band gap
  • CRequired avalanche operation
  • DOptical emission
Report an error
Correct Answer: A. Metal-semiconductor majority-carrier conduction mechanism
Explanation: Schottky junction conduction is a majority-carrier process and typically gives a lower forward drop than an ordinary silicon PN diode at comparable current.
Reference: Standard electronics: Schottky forward voltage
Question 1492
Electronic Devices & CircuitsOptoelectronic Devices

A photodiode operated in photoconductive mode is normally?

  • AReverse biased
  • BStrongly forward biased
  • CShorted with no field in every case
  • DUsed only above breakdown
Report an error
Correct Answer: A. Reverse biased
Explanation: Photoconductive-mode photodiodes are reverse biased, which widens the depletion region and generally improves response speed.
Reference: Standard optoelectronics: photodiode operating modes
Question 1493
Electronic Devices & CircuitsOptoelectronic Devices

A photodiode operated at approximately zero external bias is commonly described as operating in?

  • APhotovoltaic mode
  • BAvalanche mode only
  • CSaturation mode of a BJT
  • DClass-C mode
Report an error
Correct Answer: A. Photovoltaic mode
Explanation: In photovoltaic mode, the photodiode is used with approximately zero applied bias and develops a light-dependent voltage/current, as in solar-cell operation.
Reference: Standard optoelectronics: photovoltaic mode
Question 1494
Electronic Devices & CircuitsOptoelectronic Devices

The spectral response of a photodetector describes how its sensitivity varies primarily with?

  • AWavelength of incident light
  • BCollector resistance only
  • CSupply frequency only
  • DHeat-sink size
Report an error
Correct Answer: A. Wavelength of incident light
Explanation: Spectral response specifies detector responsivity or sensitivity as a function of optical wavelength.
Reference: Standard optoelectronics: spectral response
Question 1495
Electronic Devices & CircuitsOptoelectronic Devices

An LED material must generally have a direct band gap for efficient light emission because?

  • AElectron-hole recombination can efficiently release energy as photons
  • BIt eliminates all junction current
  • CIt forces avalanche multiplication
  • DIt makes the device an ideal resistor
Report an error
Correct Answer: A. Electron-hole recombination can efficiently release energy as photons
Explanation: Direct-band-gap semiconductors allow efficient radiative electron-hole recombination without requiring a momentum-changing phonon.
Reference: Standard optoelectronics: LED materials
Question 1498
Electronic Devices & CircuitsFET & MOSFET

In an n-channel depletion MOSFET, a conducting channel can exist at VGS=0. Applying a sufficiently negative VGS generally?

  • AReduces drain current by depleting the channel
  • BAlways increases drain current
  • CHas no effect on the channel
  • DForward biases an insulated gate junction
Report an error
Correct Answer: A. Reduces drain current by depleting the channel
Explanation: A negative gate voltage repels electrons from the n-channel, depleting it and reducing drain current.
Reference: Standard electronics: depletion MOSFET
Question 1499
Electronic Devices & CircuitsFET & MOSFET

For a long-channel MOSFET in saturation, the small-signal transconductance gm indicates how strongly drain current changes with?

  • AGate-source voltage at the bias point
  • BDrain resistance only
  • CBody temperature only
  • DGate current
Report an error
Correct Answer: A. Gate-source voltage at the bias point
Explanation: MOSFET transconductance is the incremental derivative gm=∂ID/∂VGS at the operating point.
Reference: Standard electronics: MOSFET transconductance