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Questions and Answers
A PIN diode consists of a wide region of undoped semiconductor placed between p-type and n-type materials.
A PIN diode consists of a wide region of undoped semiconductor placed between p-type and n-type materials.
True
In a PIN diode, the depletion region primarily exists outside of the intrinsic region.
In a PIN diode, the depletion region primarily exists outside of the intrinsic region.
False
The generation of charge carriers in the intrinsic region of a PIN diode can occur due to applied light energy exceeding the band-gap of the semiconductor.
The generation of charge carriers in the intrinsic region of a PIN diode can occur due to applied light energy exceeding the band-gap of the semiconductor.
True
The dark current in a reverse biased photodiode is generated solely due to light exposure.
The dark current in a reverse biased photodiode is generated solely due to light exposure.
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The reverse saturation current of a PIN diode is dependent on the reverse voltage applied to it.
The reverse saturation current of a PIN diode is dependent on the reverse voltage applied to it.
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Increasing the temperature of a photodiode results in a shift of the current-voltage characteristic curve to higher drift current values.
Increasing the temperature of a photodiode results in a shift of the current-voltage characteristic curve to higher drift current values.
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The straight-line slope (m) in the current versus illumination graph of a photodiode expresses the diode's sensitivity.
The straight-line slope (m) in the current versus illumination graph of a photodiode expresses the diode's sensitivity.
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Holes in a photodiode move towards the n region when light energy is applied.
Holes in a photodiode move towards the n region when light energy is applied.
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Study Notes
PIN Diode Basics
- PIN diode structure: A p-type, intrinsic (undoped), n-type semiconductor structure. The intrinsic region increases electron-hole pair generation.
- Depletion region: Primarily located within the intrinsic region, its width remains (nearly) constant regardless of reverse bias.
- Charge carrier generation: Can be caused by incident radiation (light).
Photodiode Operation
- Reverse bias: Photodiodes operate under reverse bias.
- Minority carrier current: The generated current is due to minority carriers.
- Light absorption: If light energy exceeds the semiconductor's band gap, valence electrons gain energy, break bonds, and become free electrons.
- Electron movement: Free electrons move towards the n-region, attracted by the positive terminal. Holes move towards the p-region.
- Photon-generated carriers: These changes are measured as variations in the external signal.
I-V Characteristics of Photodiodes
- Reverse saturation current: Approximately independent of reverse voltage.
- Temperature dependence: Increases with temperature, causing parallel shifts in the characteristic curve toward higher currents.
- Light Intensity dependence: Similar effect to temperature increase—increased light intensity (milliwatts) increases current—keeping temperature constant.
- Dark (thermal) current: Small current generated in the absence of light; due to thermal energy.
Photodiode Sensitivity
- Graph of reverse current (IR) vs. illumination (E, lux): A linear relationship, IR = mE, where 'm' is the slope and represents diode sensitivity.
- Sensitivity (m): Important parameter of a photodiode, reflecting how strongly the reverse current changes due to light. The greater the sensitivity the more accurate the response to light changes will be.
- Reverse Current vs Reverse Voltage: For a given reverse voltage, increased illumination (light) leads to an increase in reverse current through the PN junction.
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Description
This quiz covers the fundamentals of PIN diodes, focusing on their structure and the operation of photodiodes under reverse bias. Additionally, it includes concepts like charge carrier generation, light absorption, and I-V characteristics. Test your understanding of these critical semiconductor devices.
