Ch 6: Photodiodes and Optical Sensors Flashcards
Q: What is a photodiode?
A: A semiconductor device that converts light into an electrical current.
Q: What is the photovoltaic mode of a photodiode?
A: A mode where the photodiode generates voltage in response to light without external bias.
Q: What is the photoconductive mode of a photodiode?
A: A mode where the photodiode operates with reverse bias to increase sensitivity and speed.
Q: What is responsivity in optical sensors?
A: The ratio of output electrical signal to input optical power, measured in A/W (amperes per watt).
Q: How does a phototransistor differ from a photodiode?
A: A phototransistor amplifies the current generated by light, providing higher output signals.
Q: What is a solar cell?
A: A large-area photodiode designed to convert sunlight into electrical energy.
Q: What is the dark current in a photodiode?
A: The small current that flows through the photodiode in the absence of light.
Q: What are avalanche photodiodes?
A: Highly sensitive photodiodes that use avalanche multiplication to amplify the signal.
Q: What is spectral response?
A: The range of wavelengths a photodiode can detect effectively.
Q: Define quantum efficiency in optical sensors.
A: The ratio of the number of charge carriers generated to the number of incident photons.
Q: What is a fiber optic sensor?
A: A sensor that uses optical fibers to transmit light and measure physical parameters.
Q: What is total internal reflection in optical sensors?
A: A phenomenon where light is completely reflected within a medium, used in fiber optics.
Q: How are LEDs used in optical sensors?
A: As light sources to illuminate the target or medium being measured.
Q: How does a photodiode array work?
A: It consists of multiple photodiodes used to detect spatial distribution of light.
Q: What is the primary use of LDRs (light-dependent resistors)?
A: To detect light intensity in applications like night lighting.
