ETC EngineeringMCQs
Home

Optoelectronic Devices MCQs

Practice Optoelectronic Devices MCQs with four options, answers and explanations for focused Electronics & Telecommunication Engineering revision.

Question 1
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 2
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 3
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 4
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 5
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 6
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 7
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