Photodiode Working Principle Characteristics and Applications

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This article discusses what is a photodiode, working principle of photodiode, modes of operation, features, V-I characteristics and its applications

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Photodiode Working Principle, Characteristics and Applications

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http://www.elprocus.com/ Photodiode Working Principle, Characteristics and Applications Introduction: A photodiode is a PN-junction diode that consumes light energy to produce electric current. Sometimes it is also called as photo-detector, a light detector, and photo-sensor. These diodes are particularly designed to work in reverse bias condition, it means that the P-side of the photodiode is associated with the negative terminal of the battery and n-side is connected to the positive terminal of the battery.

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http://www.elprocus.com/ Photodiode Working Principle, Characteristics and Applications A photodiode is one type of light detector, used to convert the light into current or voltage based on the mode of operation of the device. It comprises of optical filters, built-in lenses and also surface areas. These diodes have a slow response time when the surface area of the photodiode increases. Photodiodes are alike to regular semiconductor diodes. What is a Photodiode

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http://www.elprocus.com/ Photodiode Working Principle, Characteristics and Applications What is a Photodiode They may be either visible to let light reach the delicate part of the device.   Several diodes intended for use exactly as a photodiode will also use a PIN junction somewhat than the usual PN junction.

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http://www.elprocus.com/ Photodiode Working Principle, Characteristics and Applications What is a Photodiode Some photodiodes will look like a light emitting diode. They have two terminals coming from the end.  The smaller end of the diode is the cathode terminal. While the longer end of the diode is the anode terminal.

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http://www.elprocus.com/ Photodiode Working Principle, Characteristics and Applications What is a Photodiode See the following schematic diagram for the anode and cathode side. Under forward bias condition, conventional current will flow from the anode to the cathode, following the arrow in the diode symbol. Photocurrent flows in the reverse direction.

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http://www.elprocus.com/ Photodiode Working Principle, Characteristics and Applications What is a Photodiode Photodiode

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http://www.elprocus.com/ Photodiode Working Principle, Characteristics and Applications Types of Photodiode Although there are numerous types of photodiode available in the market . They all works on the same basic principles, though some are improved by other effects. The working of different types of photodiodes work in a slightly different way. But the basic operation of these diodes remains the same.

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http://www.elprocus.com/ Photodiode Working Principle, Characteristics and Applications PN Photodiode Schottky Photo Diode PIN Photodiode Avalanche Photodiode Types of Photodiode The types of the photodiodes can be classified based on its construction and functions as follows.

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http://www.elprocus.com/ Photodiode Working Principle, Characteristics and Applications Types of Photodiode These diodes are widely used in different applications . where the detection of the presence of light, colour, position, intensity is required.

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http://www.elprocus.com/ Photodiode Working Principle, Characteristics and Applications Types of Photodiode The linearity of the diode is good with respect to incident light Noise is low. The response is wide spectral Rugged mechanically Light weight and compact Long life The main features of these diodes include the following.

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http://www.elprocus.com/ Photodiode Working Principle, Characteristics and Applications The required materials to make a photodiode and the range of electromagnetic spectrum wavelength range includes the following For silicon material: The electromagnetic spectrum wavelength range will be (190-1100) nm For Germanium material: The electromagnetic spectrum wavelength range will be (400-1700) nm For Indium gallium arsenide material: The electromagnetic spectrum wavelength range will be (800-2600) nm Materials to Make a Photodiode

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http://www.elprocus.com/ Photodiode Working Principle, Characteristics and Applications Materials to Make a Photodiode For Lead (II) sulfide material: The electromagnetic spectrum wavelength range will be <1000-3500) nm For Mercury, cadmium Telluride material: The electromagnetic spectrum wavelength range will be (400-14000) nm Because of their better band gap, Si-based photodiodes produce lower noise than Ge-based photodiodes.

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http://www.elprocus.com/ Photodiode Working Principle, Characteristics and Applications Working of Photodiode When a photon of ample energy strikes the diode. It makes a couple of an electron-hole. This mechanism is also called as the inner photoelectric effect. If the absorption arises in the depletion region junction. Then the carriers are removed from the junction by the inbuilt electric field of the depletion region. 

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http://www.elprocus.com/ Photodiode Working Principle, Characteristics and Applications Working of Photodiode The holes in the region move toward the anode, and electrons move toward the cathode, and a photocurrent will be generated. The entire current through the diode is the sum of the absence of light and the photocurrent. So the absent current must be reduced to maximize the sensitivity of the device.

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http://www.elprocus.com/ Photodiode Working Principle, Characteristics and Applications Working of Photodiode PN Junction Diode

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http://www.elprocus.com/ Photodiode Working Principle, Characteristics and Applications Modes of Operation The operating modes of the photodiode include three modes, namely Photovoltaic mode. Photoconductive mode. Avalanche diode mode.

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http://www.elprocus.com/ Photodiode Working Principle, Characteristics and Applications Photovoltaic Mode: This mode is also known as zero bias mode. In which a voltage is produced by the lightened photodiode. It gives a very small dynamic range & non-linear necessity of the voltage formed.

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http://www.elprocus.com/ Photodiode Working Principle, Characteristics and Applications Photoconductive Mode The photodiode used in this photoconductive mode is more usually reverse biased. The reverse voltage application will increase the depletion layer’s width. Which in turn decreases the response time & the junction capacitance. This mode is too fast and displays electronic noise.

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http://www.elprocus.com/ Photodiode Working Principle, Characteristics and Applications Avalanche Diode Mode Avalanche diodes operate in a high reverse bias condition. which permits multiplication of an avalanche breakdown to each photo-produced electron-hole pair. This outcome in an internal gain in the photodiode, which slowly increases the device response.

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http://www.elprocus.com/ Photodiode Working Principle, Characteristics and Applications V-I Characteristics of Photodiode A photodiode continually operates in a reverse bias mode. The photocurrent is nearly independent of reverse bias voltage which is applied.  For zero luminance, the photocurrent is almost zero excluding for small dark current. 

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http://www.elprocus.com/ Photodiode Working Principle, Characteristics and Applications V-I Characteristics of Photodiode It is of the order of nano amperes. As optical power rises the photo current also rises linearly.  The max photocurrent is incomplete by the power dissipation of the photo diode.

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http://www.elprocus.com/ Photodiode Working Principle, Characteristics and Applications V-I Characteristics of Photodiode The characteristics of the photodiode are shown clearly in the following figure.

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http://www.elprocus.com/ Photodiode Working Principle, Characteristics and Applications Applications of Photodiode The applications of photodiodes involve in similar applications of photodetectors like charge-coupled devices, photoconductors, and photomultiplier tubes. These diodes are used in consumer electronics devices like smoke detectors, compact disc players, televisions and remote controls in VCRs. It uses in consumer devices like clock radios, camera light meters, and street lights.

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http://www.elprocus.com/ Photodiode Working Principle, Characteristics and Applications Applications of Photodiode Photoconductors are more frequently used rather than photodiodes. Photodiodes are frequently used for exact measurement of the intensity of light in science & industry. Generally, they have an enhanced, more linear response than photoconductors.

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http://www.elprocus.com/ Photodiode Working Principle, Characteristics and Applications Applications of Photodiode Photodiodes are also widely used in numerous medical applications like instruments to analyze samples, detectors for computed tomography and also used in blood gas monitors. These diodes are much faster & more complex than normal PN junction diodes. It is frequently used for lighting regulation and in optical communications.

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http://www.elprocus.com/ Photodiode Working Principle, Characteristics and Applications A  photodiode is a kind of light detector , which involves the conversion of light into voltage or current, based on the mode of operation of the device. A photodiode is a semi-conductor device, with a p-n junction and an intrinsic layer between p and n layers. Conclusion

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