12-01-2013, 04:52 PM
Photodiode
[attachment=46821]
• What is a Photodiode?
Photodiodes are P-N junctions specifically designed to optimize their inherent photosensitivity. Photodiodes can be used two ways -- in a photovoltaic (here it becomes a current source when illuminated -- see solar cell), or photoconductive role. To use a photodiode in its photoconductive mode, the photodiode is reverse-biased; the photodiode will then allow a current to flow when it is illuminated.
• Working of the Circuit:
In this circuit, DC voltage is applied by the battery and desired voltage is acquired by the potential divider. This voltage is further amplified by the power amplifier and is supplied to the bulb. A voltmeter is also connected across the lamp to measure the potential difference across it. The bulb is placed close to the photodiode whose characteristics are to be measured in accordance with the light intensity of the bulb. Output current from the photodiode is in degrees of microamperes, so it is amplified by the current amplifier and the final output voltage is measured by another voltmeter.
It is observed that as the potential difference across the lamp is increased, the output voltage from the photodiode also increases. This result is due to the increased conduction of the photodiode as the intensity of light falling on it increases. The table of values and the graph is shown below.
[attachment=46821]
• What is a Photodiode?
Photodiodes are P-N junctions specifically designed to optimize their inherent photosensitivity. Photodiodes can be used two ways -- in a photovoltaic (here it becomes a current source when illuminated -- see solar cell), or photoconductive role. To use a photodiode in its photoconductive mode, the photodiode is reverse-biased; the photodiode will then allow a current to flow when it is illuminated.
• Working of the Circuit:
In this circuit, DC voltage is applied by the battery and desired voltage is acquired by the potential divider. This voltage is further amplified by the power amplifier and is supplied to the bulb. A voltmeter is also connected across the lamp to measure the potential difference across it. The bulb is placed close to the photodiode whose characteristics are to be measured in accordance with the light intensity of the bulb. Output current from the photodiode is in degrees of microamperes, so it is amplified by the current amplifier and the final output voltage is measured by another voltmeter.
It is observed that as the potential difference across the lamp is increased, the output voltage from the photodiode also increases. This result is due to the increased conduction of the photodiode as the intensity of light falling on it increases. The table of values and the graph is shown below.