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A photodiode is a semiconductor diode that functions as a photodetector. Photodiodes are packaged with either a window or optical fibre connection, to let in the light to the sensitive part of the device. They may also be used without a window to detect vacuum UV or X-rays. Image File history File linksMetadata Download high-resolution version (1314x1298, 402 KB) Photodiode close-up. ...
Image File history File linksMetadata Download high-resolution version (1314x1298, 402 KB) Photodiode close-up. ...
Image File history File links Download high resolution version (187x946, 48 KB)Photodiode File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ...
Image File history File links Download high resolution version (187x946, 48 KB)Photodiode File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ...
A semiconductor is a solid whose electrical conductivity is in between that of a conductor and that of an insulator, and can be controlled over a wide range, either permanently or dynamically. ...
Closeup of the image below, showing the square shaped semiconductor crystal various semiconductor diodes, below a bridge rectifier Structure of a vacuum tube diode In electronics, a diode is a two-terminal component, almost always one that has electrical properties which vary depending on the direction of flow of charge...
Photosensors or photodetectors appear in several varieties: Photoresistors or Light Dependant Resistors (LDR) which change resistance when illuminated Photovoltaic cells or solar cells which produce a voltage and supply an electric current when illuminated Photodiodes which can operate in photovoltaic mode or photoconductive mode Phototubes containing a photocathode which emits...
Optical fibers An optical fiber (or fibre) is a glass or plastic fiber designed to guide light along its length. ...
Ultraviolet (UV) radiation is electromagnetic radiation of a wavelength shorter than that of the visible region, but longer than that of soft X-rays. ...
An X-ray picture (radiograph), taken by Wilhelm Röntgen in 1896, of his wife, Anna Bertha Ludwigs[1] hand X-rays (or Röntgen rays) are a form of electromagnetic radiation with a wavelength in the range of 10 to 0. ...
A phototransistor is in essence nothing more than a bipolar transistor that is encased in a transparent case so that light can reach the base-collector junction. The phototransistor works like a photodiode, but with a much higher responsivity for light, because the electrons that are generated by photons in the base-collector junction are injected into the base, and this current is then amplified by the transistor operation. However, a phototransistor has a slower response time than a photodiode. The schematic symbols for pnp_ and npn_type BJTs. ...
For other uses, see Light (disambiguation). ...
A p-n junction is formed by combining N-type and P-type semiconductors together in very close contact. ...
Responsivity: In a photodetector, the ratio of the electrical output to the optical input. ...
Quick Reference Guide
Most Photodiodes will look like the picture to the right, that is, similar to a Light Emitting Diode. They will have two leads, or wires, coming from the bottom. The shorter end of the two is the cathode, while the longer end is the anode. See below for a schematic drawing of the anode and cathode side. Current will pass from the anode to the cathode, basically following the arrow.
Principle of operation A photodiode is a p-n junction or p-i-n structure. When a photon of sufficient energy strikes the diode, it excites an electron thereby creating a mobile electron and a positively charged electron hole. If the absorption occurs in the junction's depletion region, or one diffusion length away from it, these carriers are swept from the junction by the built-in field of the depletion region, producing a photocurrent. A p-n junction is formed by combining N-type and P-type semiconductors together in very close contact. ...
In modern physics the photon is the elementary particle responsible for electromagnetic phenomena. ...
Photodiodes can be used under either zero bias (photovoltaic mode) or reverse bias (photoconductive mode). In zero bias, light falling on the diode causes a current across the device, leading to forward bias which in turn induces "dark current" in the opposite direction to the photocurrent. This is called the photovoltaic effect, and is the basis for solar cells — in fact, a solar cell is just a large number of big photodiodes. In electrical engineering, the term bias has the following meanings: A systematic deviation of a value from a reference value. ...
A p-n junction is formed by combining N-type and P-type semiconductors together in very close contact. ...
A solar cell, or photovoltaic cell, is a semiconductor device consisting of a large-area p-n junction diode, which, in the presence of sunlight is capable of generating usable electrical energy. ...
A solar cell, made from a monocrystalline silicon wafer A solar cell or photovoltaic cell is a device that converts light energy into electrical energy. ...
Reverse bias induces only little current (known as saturation or back current) along its direction. But a more important effect of reverse bias is widening of the depletion layer (therefore expanding the reaction volume) and strengthening the photocurrent. Circuits based on this effect are more sensitive to light than ones based on the photovoltaic effect and also tend to have lower capacitance, which improves the speed of their time response. On the other hand, the photovoltaic mode tends to exhibit less electronic noise. Capacitance is a measure of the amount of electric charge stored (or separated) for a given electric potential. ...
Avalanche photodiodes have a similar structure, but they are operated with much higher reverse bias. This allows each photo-generated carrier to be multiplied by avalanche breakdown, resulting in internal gain within the photodiode, which increases the effective responsivity of the device. Avalanche photodiodes (APDs) are photodetectors that can be regarded as the semiconductor analog to photomultipliers. ...
Avalanche breakdown is a phenomenon that can occur in both insulating and semiconducting materials. ...
Materials The material used to make a photodiode is critical to defining its properties, because only photons with sufficient energy to excite electrons across the material's bandgap will produce significant photocurrents. In modern physics the photon is the elementary particle responsible for electromagnetic phenomena. ...
For other uses, see Electron (disambiguation). ...
In solid state physics and related applied fields, the band gap is the energy difference between the top of the valence band and the bottom of the conduction band in insulators and semiconductors. ...
Materials commonly used to produce photodiodes include:
Because of their greater bandgap, silicon-based photodiodes generate less noise than germanium-based photodiodes, but germanium photodiodes must be used for wavelengths longer than approximately 1 µm. Not to be confused with Silicone. ...
General Name, Symbol, Number germanium, Ge, 32 Chemical series metalloids Group, Period, Block 14, 4, p Appearance grayish white Standard atomic weight 72. ...
Indium gallium arsenide (InGaAs) is a semiconductor composed of indium, gallium and arsenic. ...
Lead sulfide (British/Commonwealth English sulphide) is a chemical compound PbS, most often purified from the mineral galena. ...
Since transistors and ICs are made of semiconductors, and contain P-N junctions, almost every active component is potentially a photodiode. Many components, especially those sensitive to small currents, will not work correctly if illuminated, due to the induced photocurrents. In most components this is not desired, so they are placed in an opaque housing. Since housings are not completely opaque to X-rays or other high energy radiation, these can still cause many ICs to malfunction due to induced photo-currents.
Features Critical performance parameters of a photodiode include: - responsivity
- The ratio of generated photocurrent to incident light power, typically expressed in A/W when used in photoconductive mode. The responsivity may also be expressed as a quantum efficiency, or the ratio of the number of photogenerated carriers to incident photons and thus a unitless quantity.
- dark current
- The current through the photodiode in the absence of light, when it is operated in photoconductive mode. The dark current includes photocurrent generated by background radiation and the saturation current of the semiconductor junction. Dark current must be accounted for by calibration if a photodiode is used to make an accurate optical power measurement, and it is also a source of noise when a photodiode is used in an optical communication system.
- noise-equivalent power
- (NEP) The minimum input optical power to generate photocurrent, equal to the rms noise current in a 1 hertz bandwidth. The related characteristic detectivity (D) is the inverse of NEP, 1/NEP; and the specific detectivity (
 ) is the detectivity normalized to the area (A) of the photodetector,  . The NEP is roughly the minimum detectable input power of a photodiode. When a photodiode is used in an optical communication system, these parameters contribute to the sensitivity of the optical receiver, which is the minimum input power required for the receiver to achieve a specified bit error ratio. Responsivity: In a photodetector, the ratio of the electrical output to the optical input. ...
For other uses, see Ampere (disambiguation). ...
For other uses, see Watt (disambiguation). ...
A graph showing variation of quantum efficiency with wavelength of the CCD chips in the Hubble Space Telescopes Wide Field and Planetary Camera 2. ...
Dark current is the constant response exhibited by a receptor of radiation during periods when it is not actively being exposed to light. ...
calibration refers to the process of determining the relation between the output (or response) of a measuring instrument and the value of the input quantity or attribute, a measurement standard. ...
Associated with all electronic circuits is noise. ...
Noise-equivalent power (NEP) is the radiant power that produces a signal-to-noise ratio of unity at the output of a given optical detector at a given data-signaling rate or modulation frequency, operating wavelength, and effective noise bandwidth. ...
This article is about the SI unit of frequency. ...
The sensitivity of an electronic device, a communications system receiver, or detection device, PIN diode, is the minimum magnitude of input signal required to produce a specified output signal having a specified signal-to-noise ratio, or other specified criteria. ...
In telecommunication, an error ratio is the ratio of the number of bits, elements, characters, or blocks incorrectly received to the total number of bits, elements, characters, or blocks sent during a specified time interval. ...
Applications ffff
 Photodiode schematic symbol P-N photodiodes are used in similar applications to other photodetectors, such as photoconductors, charge-coupled devices, and photomultiplier tubes. Image File history File links Photodiode_symbol. ...
Image File history File links Photodiode_symbol. ...
Photosensors or photodetectors appear in several varieties: Photoresistors or Light Dependant Resistors (LDR) which change resistance when illuminated Photovoltaic cells or solar cells which produce a voltage and supply an electric current when illuminated Photodiodes which can operate in photovoltaic mode or photoconductive mode Phototubes containing a photocathode which emits...
A photoresistor is an electronic component whose resistance decreases with increasing incident light intensity. ...
A specially developed CCD used for ultraviolet imaging in a wire bonded package. ...
Photomultipliers, or photomultiplier tubes (PMT) are extremely sensitive detectors of light in the ultraviolet, visible and near infrared. ...
Photodiodes are used in consumer electronics devices such as compact disc players, smoke detectors, and the receivers for remote controls in VCRs and televisions. Consumer electronics is a term used to describe the category of electronic equipment intended for everyday use by people, the consumers. ...
CD redirects here. ...
A smoke detector or smoke alarm is a device that detects smoke and issues an alarm to alert nearby people that there is a potential fire. ...
The video cassette recorder (or VCR, less popularly video tape recorder) is a type of video tape recorder that uses removable cassettes containing magnetic tape to record audio and video from a television broadcast so it can be played back later. ...
In other consumer items such as camera light meters, clock radios (the ones that dim the display when it's dark) and street lights, photoconductors are often used rather than photodiodes, although in principle either could be used. This article is about the photographing device. ...
A photoresistor is an electronic component whose resistance decreases with increasing incident light intensity. ...
Photodiodes are often used for accurate measurement of light intensity in science and industry. They generally have a better, more linear response than photoconductors.
They are also widely used in various medical applications, such as detectors for computed tomography (coupled with scintillators) or instruments to analyze samples (immunoassay). They are also used in blood gas monitors. negron305 Cat scan redirects here. ...
A scintillator is a device or substance that absorbs high energy (ionizing) electromagnetic or charged particle radiation then, in response, fluoresces photons at a characteristic Stokes-shifted (longer) wavelength, releasing the previously absorbed energy. ...
An immunoassay is a biochemical test that measures the concentration of a substance in a biological liquid, typically serum or urine, using the reaction of an antibody or antibodies to its antigen. ...
A portable saturometer (for emergencies) Measure by optic properties through the nail A blood gas monitor is a medical device that measures the amount of a dissolved gas in a patients blood. ...
PIN diodes are much faster and more sensitive than ordinary p-n junction diodes, and hence are often used for optical communications and in lighting regulation. Layers of a PIN diode PIN diode is a diode with a wide, undoped intrinsic semiconductor region between p-type semiconductor and n-type semiconductor regions. ...
Optical communication is any form of telecommunication that uses light as the transmission medium. ...
P-N photodiodes are not used to measure extremely low light intensities. Instead, if high sensitivity is needed, avalanche photodiodes, intensified charge-coupled devices or photomultiplier tubes are used for applications such as astronomy, spectroscopy, night vision equipment and laser range finding. Avalanche photodiodes (APDs) are photodetectors that can be regarded as the semiconductor analog to photomultipliers. ...
An intensified charged-coupled device (ICCD) is a CCD that is fiber-optically connected to a micro-channel plate (MCP) to increase the sensitivity. ...
Photomultipliers, or photomultiplier tubes (PMT) are extremely sensitive detectors of light in the ultraviolet, visible and near infrared. ...
For other uses, see Astronomy (disambiguation). ...
Animation of the dispersion of light as it travels through a triangular prism. ...
An American soldier uses a helmet mounted night vision device A night vision device (NVD) is an optical instrument that allows images to be produced in levels of light approaching total darkness. ...
A laser range-finder, or LIDAR (LIght Detection And Ranging), is a device which uses a laser beam in order to determine the distance to an opaque object. ...
Comparison with photomultipliers Advantages compared to photomultipliers: Photomultipliers, or photomultiplier tubes (PMT) are extremely sensitive detectors of light in the ultraviolet, visible and near infrared. ...
- Excellent linearity of output current as a function of incident light
- Spectral response from 190 nm to 1100 nm (silicon), longer wavelengths with other semiconductor materials
- Low noise
- Ruggedized to mechanical stress
- Low cost
- Compact and light weight
- Long lifetime
- High quantum efficiency, typically 80%
- No high voltage required
Disadvantages compared to photomultipliers: Not to be confused with Silicone. ...
For other uses, see Wavelength (disambiguation). ...
Semiconductor materials are insulators at absolute zero temperature that conduct electricity in a limited way at room temperature (see also Semiconductor). ...
A graph showing variation of quantum efficiency with wavelength of the CCD chips in the Hubble Space Telescopes Wide Field and Planetary Camera 2. ...
Photomultipliers, or photomultiplier tubes (PMT) are extremely sensitive detectors of light in the ultraviolet, visible and near infrared. ...
- Small area
- No internal gain (except avalanche photodiodes, but their gain is typically 10²–10³ compared to up to 108 for the photomultiplier)
- Much lower overall sensitivity
- Photon counting only possible with specially designed, usually cooled photodiodes, with special electronic circuits
- Response time for many designs is slower
Avalanche photodiodes (APDs) are photodetectors that can be regarded as the semiconductor analog to photomultipliers. ...
P-N vs. P-I-N Photodiodes - Due to the intrinsic layer, a PIN photodiode must be reverse biased (Vr). The Vr increases the depletion region allowing a larger volume for electron-hole pair production, and reduces the capacitance thereby increasing the bandwidth.
- The Vr also introduces noise current, which reduces the S/N ratio. Therefore, a reverse bias is recommended for higher bandwidth applications and/or applications where a wide dynamic range is required.
- A PN photodiode is more suitable for lower light applications because it allows for unbiased operation.
Photodiode array Hundreds or thousands (up to 2048) photodiodes of typical sensitive area 0.025mmx1mm each arranged as a one-dimensional array, which can be used as a position sensor. One advantage of photodiode arrays (PDAs) is that they allow for high speed parallel read out since the driving electronics may not be built in like a traditional CMOS or CCD sensor. A position sensor is any device that enables position measurement. ...
See also This article is about the engineering discipline. ...
This article or section does not adequately cite its references or sources. ...
For other uses, see Infrared (disambiguation). ...
Optoelectronics is the study and application of electronic devices that interact with light, and thus is usually considered a sub-field of photonics. ...
An opto-isolator integrated circuit. ...
Semiconductor devices are electronic components that exploit the electronic properties of semiconductor materials, principally silicon, germanium, and gallium arsenide. ...
A solar cell, made from a monocrystalline silicon wafer A solar cell or photovoltaic cell is a device that converts light energy into electrical energy. ...
A transducer is a device, usually electrical or electronic, that converts one type of energy to another. ...
A light meter is a device used to measure the amount of light. ...
References - Portions of this article are adapted from Federal Standard 1037C and from the FAA Glossary of Optical Communications Terms
This article contains material from the Federal Standard 1037C, which, as a work of the United States Government, is in the public domain. Federal Standard 1037C, entitled Telecommunications: Glossary of Telecommunication Terms is a United States Federal Standard, issued by the General Services Administration pursuant to the Federal Property and Administrative Services Act of 1949, as amended. ...
Federal Standard 1037C, entitled Telecommunications: Glossary of Telecommunication Terms is a United States Federal Standard, issued by the General Services Administration pursuant to the Federal Property and Administrative Services Act of 1949, as amended. ...
A work of the United States government, as defined by United States copyright law, is a work prepared by an officer or employee of the U.S. government as part of that persons official duties. ...
The public domain comprises the body of all creative works and other knowledge—writing, artwork, music, science, inventions, and others—in which no person or organization has any proprietary interest. ...
- Gowar, John, Optical Communication Systems, 2 ed., Prentice-Hall, Hempstead UK, 1993 (ISBN 0-13-638727-6)
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