第一篇：電子信息工程3_低頻功率放大器(英文翻譯)_2010.5.30

大連理工大學(xué)城市學(xué)院

本科生畢業(yè)設(shè)計（論文）

外文翻譯

學(xué) 院：電子與自動化學(xué)院 專 業(yè)： 電子信息工程 學(xué) 生： 丁 琳 指導(dǎo)教師： 馬 彧 完成日期： 2010年5月30日

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Light-emitting diode Discoveries and early devices

Electroluminescence was discovered in 1907 by the British experimenter H.J.Round of Marconi Labs, using a crystal of silicon carbide and a cat's-whisker detector.Russian Oleg Vladimirovich Losev independently reported on the creation of an LED in 1927.His research was distributed in Russian, German and British scientific journals, but no practical use was made of the discovery for several decades.Rubin Braunstein of the Radio Corporation of America reported on infrared emission from gallium arsenide(GaAs)and other semiconductor alloys in 1955.Braunstein observed infrared emission generated by simple diode structures using gallium antimonide(GaSb), GaAs, indium phosphide(InP), and silicon-germanium(SiGe)alloys at room temperature and at 77 kelvin.In 1961, experimenters Robert Biard and Gary Pittman working at Texas Instruments, found that GaAs emitted infrared radiation when electric current was applied and received the patent for the infrared LED.The first practical visible-spectrum(red)LED was developed in 1962 by Nick Holonyak Jr., while working at General Electric Company.Holonyak is seen as the “father of the light-emitting diode”.M.George Craford, a former graduate student of Holonyak, invented the first yellow LED and improved the brightness of red and red-orange LEDs by a factor of ten in 1972.In 1976, T.P.Pearsall created the first high-brightness, high efficiency LEDs for optical fiber telecommunications by inventing new semiconductor materials specifically adapted to optical fiber transmission wavelengths.Up to 1968 visible and infrared LEDs were extremely costly, on the order of US $200 per unit, and so had little practical application.The Monsanto Company was the first organization to mass-produce visible LEDs, using gallium arsenide phosphide in 1968 to produce red LEDs suitable for indicators.Hewlett Packard(HP)introduced LEDs in 1968, initially using GaAsP supplied by Monsanto.The technology proved to have major applications for alphanumeric displays and was integrated into HP's early handheld calculators.In the 1970s commercially successful LED devices at under five cents each were produced by Fairchild Optoelectronics.These devices

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employed compound semiconductor chips fabricated with the planar process invented by Dr.Jean Hoerni at Fairchild Semiconductor.The combination of planar processing for chip fabrication and innovative packaging techniques enabled the team at Fairchild led by optoelectronics pioneer Thomas Brandt to achieve the necessary cost reductions.These techniques continue to be used by LED producers.Continuing development

The first high-brightness blue LED was demonstrated by Shuji Nakamura of Nichia Corporation and was based on InGaN borrowing on critical developments in GaN nucleation on sapphire substrates and the demonstration of p-type doping of GaN which were developed by Isamu Akasaki and H.Amano in Nagoya.In 1995, Alberto Barbieri at the Cardiff University Laboratory(GB)investigated the efficiency and reliability of high-brightness LEDs and demonstrated a very impressive result by using a transparent contact made of indium tin oxide(ITO)on(AlGaInP/GaAs)LED.The existence of blue LEDs and high efficiency LEDs quickly led to the development of the first white LED, which employed a Y3Al5O12:Ce, or “YAG”, phosphor coating to mix yellow(down-converted)light with blue to produce light that appears white.Nakamura was awarded the 2006 Millennium Technology Prize for his invention.The development of LED technology has caused their efficiency and light output to increase exponentially, with a doubling occurring about every 36 months since the 1960s, in a way similar to Moore's law.The advances are generally attributed to the parallel development of other semiconductor technologies and advances in optics and material science.This trend is normally called Haitz's Law after Dr.Roland Haitz.In February 2008, Bilkent university in Turkey reported 300 lumens of visible light per watt luminous efficacy(not per electrical watt)and warm light by using nanocrystals.In January 2009, researchers from Cambridge University reported a process for growing gallium nitride(GaN)LEDs on silicon.Production costs could be reduced by 90% using six-inch silicon wafers instead of two-inch sapphire wafers.The team was led by Colin Humphreys

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Technology

Physics

Like a normal diode, the LED consists of a chip of semiconducting material doped with impurities to create a p-n junction.As in other diodes, current flows easily from the p-side, or anode, to the n-side, or cathode, but not in the reverse direction.Charge-carriers—electrons and holes—flow into the junction from electrodes with different voltages.When an electron meets a hole, it falls into a lower energy level, and releases energy in the form of a photon.The wavelength of the light emitted, and therefore its color, depends on the band gap energy of the materials forming the p-n junction.In silicon or germanium diodes, the electrons and holes recombine by a non-radiative transition which produces no optical emission, because these are indirect band gap materials.The materials used for the LED have a direct band gap with energies corresponding to near-infrared, visible or near-ultraviolet light.LED development began with infrared and red devices made with gallium arsenide.Advances in materials science have made possible the production of devices with ever-shorter wavelengths, producing light in a variety of colors.LEDs are usually built on an n-type substrate, with an electrode attached to the p-type layer deposited on its surface.P-type substrates, while less common, occur as well.Many commercial LEDs, especially GaN/InGaN, also use sapphire substrate.Most materials used for LED production have very high refractive indices.This means that much light will be reflected back into the material at the material/air surface interface.Therefore Light extraction in LEDs is an important aspect of LED production, subject to much research and development.Efficiency and operational parameters

Typical indicator LEDs are designed to operate with no more than

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30–60 milliwatts [mW] of electrical power.Around 1999, Philips Lumileds introduced power LEDs capable of continuous use at one watt [W].These LEDs used much larger semiconductor die sizes to handle the large power inputs.Also, the semiconductor dies were mounted onto metal slugs to allow for heat removal from the LED die.One of the key advantages of LED-based lighting is its high efficiency, as measured by its light output per unit power input.White LEDs quickly matched and overtook the efficiency of standard incandescent lighting systems.In 2002, Lumileds made five-watt LEDs available with a luminous efficacy of 18–22 lumens per watt [lm/W].For comparison, a conventional 60–100 W incandescent lightbulb produces around 15 lm/W, and standard fluorescent lights produce up to 100 lm/W.A recurring problem is that efficiency will fall dramatically for increased current.This effect is known as droop and effectively limits the light output of a given LED, increasing heating more than light output for increased current.In September 2003, a new type of blue LED was demonstrated by the company Cree, Inc.to provide 24 mW at 20 milliamperes [mA].This produced a commercially packaged white light giving 65 lm/W at 20 mA, becoming the brightest white LED commercially available at the time, and more than four times as efficient as standard incandescents.In 2006 they demonstrated a prototype with a record white LED luminous efficacy of 131 lm/W at 20 mA.Also, Seoul Semiconductor has plans for 135 lm/W by 2007 and 145 lm/W by 2008, which would be approaching an order of magnitude improvement over standard incandescents and better even than standard fluorescents.Nichia Corporation has developed a white LED with luminous efficacy of 150 lm/W at a forward current of 20 mA.It should be noted that high-power(≥ 1 W)LEDs are necessary for practical general lighting applications.Typical operating currents for these devices begin at 350 mA.Note that these efficiencies are for the LED chip only, held at low temperature in a lab.In a lighting application, operating at higher temperature and with drive circuit losses, efficiencies are much lower.United States Department of Energy(DOE)testing of commercial LED lamps designed to replace incandescent lamps or CFLs showed that average efficacy was still about 46 lm/W in 2009(tested

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performance ranged from 17 lm/W to 79 lm/W)[32].Cree issued a press release on February 3, 2010 about a laboratory prototype LED achieving 208 lumens per watt at room temperature.The correlated color temperature was reported to be 4579 K.[33]

Lifetime and failure Main article: List of LED failure modes

Solid state devices such as LEDs are subject to very limited wear and tear if operated at low currents and at low temperatures.Many of the LEDs produced in the 1970s and 1980s are still in service today.Typical lifetimes quoted are 25,000 to 100,000 hours but heat and current settings can extend or shorten this time significantly.[34]

The most common symptom of LED(and diode laser)failure is the gradual lowering of light output and loss of efficiency.Sudden failures, although rare, can occur as well.Early red LEDs were notable for their short lifetime.With the development of high-power LEDs the devices are subjected to higher junction temperatures and higher current densities than traditional devices.This causes stress on the material and may cause early light output degradation.To quantitatively classify lifetime in a standardized manner it has been suggested to use the terms L75 and L50 which is the time it will take a given LED to reach 75% and 50% light output respectively.[35] L50 is equivalent to the half-life of the LED.Like other lighting devices, LED performance is temperature dependent.Most manufacturers’ published ratings of LEDs are for an operating temperature of 25°C.LEDs used outdoors, such as traffic signals or in-pavement signal lights, and that are utilized in climates where the temperature within the luminaire gets very hot, could result in low signal intensities or even failure[36].LEDs maintain consistent light output even in cold temperatures, unlike traditional lighting methods.Consequently, LED technology may be a good replacement in areas such as supermarket freezer lighting[37][38][39] and will last longer than other technologies.Because LEDs do not generate as much heat as incandescent bulbs, they are an energy-efficient technology to use in such applications such as freezers.On the other hand, because they do not generate much heat, ice and snow may build up on the LED luminaire in

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colder climates[40].This has been a problem plaguing airport runway lighting, although some research has been done to try to develop heat sink technologies in order to transfer heat to alternative areas of the luminaire.[41]

Practical use

The first commercial LEDs were commonly used as replacements for incandescent and neon indicator lamps, and in seven-segment displays, first in expensive equipment such as laboratory and electronics test equipment, then later in such appliances as TVs, radios, telephones, calculators, and even watches(see list of signal applications).These red LEDs were bright enough only for use as indicators, as the light output was not enough to illuminate an area.Later, other colors became widely available and also appeared in appliances and equipment.As the LED materials technology became more advanced, the light output was increased, while maintaining the efficiency and the reliability to an acceptable level.The invention and development of the high power white light LED led to use for illumination(see list of illumination applications).Most LEDs were made in the very common 5 mm T1? and 3 mm T1 packages, but with increasing power output, it has become increasingly necessary to shed excess heat in order to maintain reliability, so more complex packages have been adapted for efficient heat dissipation.Packages for state-of-the-art high power LEDs bear little resemblance to early LEDs.The low energy consumption, low maintenance and small size of modern LEDs has led to applications as status indicators and displays on a variety of equipment and installations.Large area LED displays are used as stadium displays and as dynamic decorative displays.Thin, lightweight message displays are used at airports and railway stations, and as destination displays for trains, buses, trams, and ferries.The single color light is well suited for traffic lights and signals, exit signs, emergency vehicle lighting, ships' lanterns and LED-based Christmas lights.In cold climates, LED traffic lights may remain snow covered.[86] Red or yellow LEDs are used in indicator and alphanumeric displays in environments where night vision must be retained: aircraft cockpits, submarine and ship bridges, astronomy

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observatories, and in the field, e.g.night time animal watching and military field use.Because of their long life and fast switching times, LEDs have been used for automotive high-mounted brake lights and truck and bus brake lights and turn signals for some time, but many vehicles now use LEDs for their rear light clusters.The use of LEDs also has styling advantages because LEDs are capable of forming much thinner lights than incandescent lamps with parabolic reflectors.The significant improvement in the time taken to light up(perhaps 0.5 s faster than an incandescent bulb)improves safety by giving drivers more time to react.It has been reported that at normal highway speeds this equals one car length increased reaction time for the car behind.White LED headlamps are beginning to make an appearance.In an dual intensity circuit(i.e.rear markers and brakes)if the LED's are not pulsed at a fast enough frequency, they can create a phantom array, where ghost images of the LED will appear if the eyes quickly scan across the array.Due to the relative cheapness of low output LEDs, they are also used in many temporary applications such as glowsticks, throwies, and the photonic textile Lumalive.Artists have also used LEDs for LED art.Weather/all-hazards radio receivers with Specific Area Message Encoding(SAME)have three LEDs: red for warnings, orange for watches, and yellow for advisories & statements whenever issued.Lighting Main article: LED lamp With the development of high efficiency and high power LEDs it has become possible to incorporate LEDs in lighting and illumination.Replacement light bulbs have been made as well as dedicated fixtures and LED lamps.LEDs are used as street lights and in other architectural lighting where color changing is used.The mechanical robustness and long lifetime is used in automotive lighting on cars, motorcycles and on bicycle lights.LEDs have been used for lighting of streets and of parking garages.In 2007, the Italian village Torraca was the first place to convert its entire illumination system to LEDs.LEDs are being used increasingly commonly for aquarium lighting.發(fā)光二極管

Particular for reef aquariums, LED lights provide an efficient light source with less heat output to help maintain optimal aquarium temperatures.LED-based aquarium fixtures also have the advantage of being manually adjustable to produce a specific color-spectrum for ideal coloration of corals, fish, and invertebrates while optimizing photosynethically active radiation(PAR)which increases growth and sustainability of photosynthetic life such as corals, anemones, clams, and macroalgae.These fixtures can be electronically programmed in order to simulate various lighting conditions throughout the day, reflecting phases of the sun and moon for a dynamic reef experience.LED fixtures typically cost up to five times as much as similarly rated fluorescent or high-intensity discharge lighting designed for reef aquariums and are not as high output to date.LEDs are also being used now in airport and heliport lighting.LED airport fixtures currently include medium intensity runway lights, runway centerline lights and obstruction lighting.LEDs are also suitable for backlighting for LCD televisions and lightweight laptop displays and light source for DLP projectors.RGB LEDs increase the color gamut by as much as 45%.Screens for TV and computer displays can be made increasingly thin using LEDs for backlighting.The lack of IR/heat radiation makes LEDs ideal for stage lights using banks of RGB LEDs that can easily change color and decrease heating from traditional stage lighting, as well as medical lighting where IR-radiation can be harmful.Since LEDs are small, durable and require little power they are used in hand held devices such as flashlights.LED strobe lights or camera flashes operate at a safe, low voltage, as opposed to the 250+ volts commonly found in xenon flashlamp-based lighting.This is particularly applicable to cameras on mobile phones, where space is at a premium and bulky voltage-increasing circuitry is undesirable.LEDs are used for infrared illumination in night vision applications including security cameras.A ring of LEDs around a video camera, aimed forward into a retroreflective background, allows chroma keying in video productions.LEDs are used for decorative lighting as well.Uses include but are not limited to indoor/outdoor decor, limousines, cargo trailers，發(fā)光二極管

conversion vans, cruise ships, RVs, boats, automobiles, and utility trucks.Decorative LED lighting can also come in the form of lighted company signage and step and aisle lighting in theaters and auditoriums.Smart lighting Light can be used to transmit broadband data, which is already implemented in IrDA standards using infrared LEDs.Because LEDs can cycle on and off millions of times per second, they can, in effect, become wireless routers for data transport.[89] Lasers can also be modulated in this manner.Sustainable lighting Efficient lighting is needed for sustainable architecture.A 13 watt LED lamp produces 450 to 650 lumens.which is equivalent to a standard 40 watt incandescent bulb.A standard 40 W incandescent bulb has an expected lifespan of 1,000 hours while an LED can continue to operate with reduced efficiency for more than 50,000 hours, 50 times longer than the incandescent bulb.Environmentally friendly options A single kilowatt-hour of electricity will generate 1.34 pounds(610 g)of CO2 emissions.[92] Assuming the average light bulb is on for 10 hours a day, a single 40-watt incandescent bulb will generate 196 pounds(89 kg)of CO2 every year.The 13-watt LED equivalent will only be responsible for 63 pounds(29 kg)of CO2 over the same time span.A building’s carbon footprint from lighting can be reduced by 68% by exchanging all incandescent bulbs for new LEDs in warm climates.In cold climates, the energy saving may be lower, since more heating would be needed to compensate for the lower temperature.LEDs are also non-toxic unlike the more popular energy efficient bulb option: the compact fluorescent a.k.a.CFL which contains traces of harmful mercury.While the amount of mercury in a CFL is small, introducing less into the environment is preferable.Economically sustainable LED light bulbs could be a cost-effective option for lighting a home or office space because of their very long lifetimes.Consumer use of LEDs as a replacement for conventional lighting system is currently hampered by the high cost and low efficiency of available products.發(fā)光二極管

2009 DOE testing results showed an average efficacy of 35 lm/W, below that of typical CFLs, and as low as 9 lm/W, worse than standard incandescents.[90] The high initial cost of the commercial LED bulb is due to the expensive sapphire substrate which is key to the production process.The sapphire apparatus must be coupled with a mirror-like collector to reflect light that would otherwise be wasted.In 2008, a materials science research team at Purdue University succeeded in producing LED bulbs with a substitute for the sapphire components.The team used metal-coated silicon wafers with a built-in reflective layer of zirconium nitride to lessen the overall production cost of the LED.They predict that within a few years, LEDs produced with their revolutionary, new technique will be competitively priced with CFLs.The less expensive LED would not only be the best energy saver, but also a very economical bulb.Non-visual applications Light has many other uses besides for seeing.LEDs are used for some of these applications.The uses fall in three groups: Communication, sensors and light matter interaction.The light from LEDs can be modulated very quickly so they are used extensively in optical fiber and Free Space Optics communications.This include remote controls, such as for TVs and VCRs, where infrared LEDs are often used.Opto-isolators use an LED combined with a photodiode or phototransistor to provide a signal path with electrical isolation between two circuits.This is especially useful in medical equipment where the signals from a low voltage sensor circuit(usually battery powered)in contact with a living organism must be electrically isolated from any possible electrical failure in a recording or monitoring device operating at potentially dangerous voltages.An optoisolator also allows information to be transferred between circuits not sharing a common ground potential.Many sensor systems rely on light as the signal source.LEDs are often ideal as a light source due to the requirements of the sensors.LEDs are used as movement sensors, for example in optical computer mice.The Nintendo Wii's sensor bar uses infrared LEDs.In pulse oximeters for measuring oxygen saturation.Some flatbed scanners use arrays of RGB LEDs rather than the typical cold-cathode fluorescent lamp as the light source.Having independent control of three illuminated colors allows the scanner to calibrate itself for more

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accurate color balance, and there is no need for warm-up.Furthermore, its sensors only need be monochromatic, since at any one point in time the page being scanned is only lit by a single color of light.Touch sensing: Since LEDs can also be used as photodiodes, they can be used for both photo emission and detection.This could be used in for example a touch-sensing screen that register reflected light from a finger or stylus.Many materials and biological systems are sensitive to, or dependent on light.Grow lights use LEDs to increase photosynthesis in plants[95] and bacteria and viruses can be removed from water and other substances using UV LEDs for sterilization Other uses are as UV curing devices for some ink and coating applications as well as LED printers.The use of LEDs is particularly interesting to plant cultivators, mainly because it is more energy efficient, less heat is produced(can damage plants close to hot lamps)and can provide the optimum light frequency for plant growth and bloom periods compared to currently used grow lights: HPS(high pressure sodium), MH(metal halide)or CFL/low-energy.It has however not replaced these grow lights due to it having a higher retail price, as mass production and LED kits develop the product will become cheaper.LEDs have also been used as a medium quality voltage reference in electronic circuits.The forward voltage drop(e.g., about 1.7 V for a normal red LED)can be used instead of a Zener diode in low-voltage regulators.Red LEDs have the flattest I/V curve above the knee;nitride-based LEDs have a fairly steep I/V curve and are not useful in this application.Although LED forward voltage is much more current-dependent than a good Zener, Zener diodes are not widely available below voltages of about 3 V.Machine vision systems often require bright and homogeneous illumination, so features of interest are easier to process.LEDs are often used to this purpose, and this field of application is likely to remain one of the major application areas until price drops low enough to make signaling and illumination applications more widespread.Barcode scanners are the most common example of machine vision, and many inexpensive ones used red LEDs instead of lasers.LEDs constitute a nearly ideal light source for machine vision systems for several reasons:

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The size of the illuminated field is usually comparatively small and machine vision systems are often quite expensive, so the cost of the light source is usually a minor concern.However, it might not be easy to replace a broken light source placed within complex machinery, and here the long service life of LEDs is a benefit.LED elements tend to be small and can be placed with high density over flat or even shaped substrates(PCBs etc.)so that bright and homogeneous sources can be designed which direct light from tightly controlled directions on inspected parts.This can often be obtained with small, inexpensive lenses and diffusers, helping to achieve high light densities with control over lighting levels and homogeneity.LED sources can be shaped in several configurations(spot lights for reflective illumination;ring lights for coaxial illumination;back lights for contour illumination;linear assemblies;flat, large format panels;dome sources for diffused, omnidirectional illumination).LEDs can be easily strobed(in the microsecond range and below)and synchronized with imaging.High power LEDs are available allowing well lit images even with very short light pulses.This is often used in order to obtain crisp and sharp ―still‖ images of quickly-moving parts.LEDs come in several different colors and wavelengths, easily allowing to use the best color for each application, where different color may provide better visibility of features of interest.Having a precisely known spectrum allows tightly matched filters to be used to separate informative bandwidth or to reduce disturbing effect of ambient light.LEDs usually operate at comparatively low working temperatures, simplifying heat management and dissipation, therefore allowing plastic lenses, filters and diffusers to be used.Waterproof units can also easily be designed, allowing for use in harsh or wet environments(food, beverage, oil industries).發(fā)光二極管

發(fā)現(xiàn)和早期設(shè)備

電致發(fā)光被發(fā)現(xiàn)于1907年由英國實驗者黃建忠回合的馬可尼實

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驗室，使用的晶體硅碳化物和急先鋒，晶須探測器。俄羅斯奧列格羅維奇洛謝夫獨立報上創(chuàng)造的1 27年的LED英寸他的研究主要分布在俄羅斯，德國和英國的科學(xué)雜志，但沒有實際使用是由幾個20年發(fā)現(xiàn)的。魯賓Braunstein在美國廣播公司報道紅外排放砷化鎵（砷化鎵）及其他半導(dǎo)體合金在1955年。Braunstein觀察紅外發(fā)射二極管產(chǎn)生的使用結(jié)構(gòu)簡單的銻化鎵（GaSb等），砷化鎵，磷化銦（磷化銦）和硅鍺（SiGe）的室內(nèi)溫度合金并在77開爾文。

1961年，實驗者和加里羅伯特皮特曼Biard在工作德州儀器，發(fā)現(xiàn)，砷化鎵紅外輻射時發(fā)出的電流應(yīng)用于紅外發(fā)光二極管，并獲得專利的。

第一個實際可見光譜（紅色）發(fā)光二極管開發(fā)于1962年由尼克Holonyak小，而在工作通用電氣公司。Holonyak是“發(fā)光二極管被視為”父親的光。喬治克拉福德，學(xué)生畢業(yè)前的Holonyak，發(fā)明了第一個黃色的LED和改善。亮度紅色的一個因素和紅色LED橙10在1972年1976年，總磷皮爾索爾創(chuàng)造了第一個高亮度，光纖波長高效率發(fā)光二極管的發(fā)明新的電信傳輸半導(dǎo)體材料特別適合于光纖。

截至到1968年的可見光和紅外發(fā)光二極管都非常昂貴，在美國以每單位200元，所以沒有什么實際應(yīng)用。的孟山都公司是第一個組織批量生產(chǎn)可見光LED，用磷化1968年砷化鎵紅色發(fā)光二極管生產(chǎn)適合指標(biāo)。惠普（惠普）介紹了LED在1968年，最初使用砷化鎵孟山都公司提供的。這項技術(shù)被證明有字母數(shù)字顯示器的主要應(yīng)用，并成為惠普的早期綜合手持計算器。在20世紀(jì)70年代商業(yè)成功的LED器件在每個5歲以下被飛兆半導(dǎo)體光電產(chǎn)品美分。這些器件采用飛兆半導(dǎo)體在赫爾尼化合物半導(dǎo)體芯片，讓工藝制造的平面博士發(fā)明的。的技術(shù)相結(jié)合的平面處理芯片制造和創(chuàng)新的封裝使得飛兆半導(dǎo)體在率領(lǐng)球隊光電先驅(qū)托馬斯勃蘭特實現(xiàn)所需費用減少。這些技術(shù)仍然是生產(chǎn)者使用的LED

持續(xù)發(fā)展

第一個高亮度藍(lán)色發(fā)光二極管被證明中村修二的日亞化學(xué)公司，發(fā)光二極管

并于基于氮化銦鎵的借貸關(guān)鍵發(fā)展對氮化鎵在藍(lán)寶石襯底上成核和發(fā)展了P的示范型氮化鎵摻雜其中赤崎勇和H.天野在名古屋。1995年，阿爾貝托巴比在加的夫大學(xué)的實驗室（GB）的調(diào)查的效率和可靠性的LED高亮度，表現(xiàn)出了非常令人印象深刻的聯(lián)系結(jié)果通過使用透明的銦錫氧化物（ITO）薄膜上（磷化鋁鎵銦/砷化鎵）的LED。藍(lán)色發(fā)光二極管存在的，高效率LED的迅速發(fā)展導(dǎo)致了第一次的白光LED，它采用的 Y 三基地5 ? 12：鈰，或“ YAG激光 “，熒光粉涂層混合下變換）輕型藍(lán)黃（生產(chǎn)出現(xiàn)白色的光。中村被授予2006年千年科技獎的發(fā)明人。

該技術(shù)的發(fā)展已引起他們的LED光輸出效率，增加指數(shù)，與20世紀(jì)60年代以來發(fā)生的36個月翻一番大約每到，在某種程度上類似摩爾定律。一般的進步歸因于其他半導(dǎo)體技術(shù)和光學(xué)和材料科學(xué)的進步并行發(fā)展。這種趨勢是通常稱為Haitz定律后，羅蘭博士Haitz。

2008年2月，比爾肯大學(xué)大學(xué)在土耳其報300瓦每流明光可見光發(fā)光效率瓦（而不是每電氣），并利用溫光納米晶體。

2009年1月，來自英國劍橋大學(xué)的研究人員報告說，為不斷發(fā)展的氮化矽（氮化鎵）LED的鎵過程。生產(chǎn)成本可以減少90％，而不是采用2英寸藍(lán)寶石晶圓6英寸硅片。該團隊由科林漢弗萊斯。

技術(shù)

物理

像一個正常的二極管，發(fā)光二極管組成的一個芯片的半導(dǎo)體材料摻雜的雜質(zhì)，以創(chuàng)造一個pn結(jié)。正如在其他二極管，電流流或容易從P端，陽極，到N端，或陰極，但不是在相反方向。電荷載體，電子和洞，從交界處流入電極具有不同的電壓。當(dāng)電子遇到一個洞，它屬于一個較低的能級，并釋放能量的一個形式的光子。

該波長的發(fā)射光，因此它的顏色，取決于帶隙能量的 PN 結(jié)的材料組成。在硅或鍺二極管中，電子和光學(xué)發(fā)射孔重組由非輻射躍遷而產(chǎn)生沒有，因為這些都是間接帶隙材料。所用的材料為LED有直接帶隙的能量相當(dāng)于近紅外，可見光或近紫外線。

發(fā)光二極管

LED的發(fā)展開始用紅色和紅外設(shè)備作出的鎵砷化物。在進展材料科學(xué)與以往任何時候都取得了波長更短的生產(chǎn)設(shè)備的可能，產(chǎn)生光的顏色不同。

發(fā)光二極管通常是建立在一個n型襯底附加于p型層的電極，在其表面沉積。P型襯底，而不太常見，也發(fā)生。許多商業(yè)的LED，尤其是氮化鎵/氮化銦鎵，還使用藍(lán)寶石襯底。

大多數(shù)材料的生產(chǎn)用于LED具有很高的折射率。這意味著，大量光將反映到在關(guān)鍵材料的背面/空氣表面界面。因此LED的光提取是一個重要方面LED生產(chǎn)，但以大量的研究和發(fā)展。

效率與操作參數(shù)

典型的LED指示燈被設(shè)計運行不超過30-60 毫瓦的電能[毫瓦]。在1999年左右，飛利浦Lumileds公司推出能夠在一個連續(xù)的使用功率LED 瓦 [我們]。這些LED采用更大的半導(dǎo)體芯片來處理大型電源輸入。此外，半導(dǎo)體芯片都是固定在金屬片上，以供熱量從LED芯片搬遷。

對LED照明的關(guān)鍵優(yōu)勢之一是它的高效率，其每單位的光輸出功率輸入測量。.白光LED的匹配，迅速超越了標(biāo)準(zhǔn)的白熾燈照明系統(tǒng)的效率。2002年，Lumileds公司作出瓦的LED可提供5 發(fā)光效率的18至22 流明每瓦[流明/瓦]。相比之下，傳統(tǒng)的60?100 W 白熾燈泡生產(chǎn)約15流明/瓦，與標(biāo)準(zhǔn)熒光燈產(chǎn)生高達100流明/ W的一個經(jīng)常發(fā)生的問題是，效率將下降為目前的大幅增加。這種效應(yīng)被稱為下垂，有效地限制了特定的LED光輸出的一，增加加熱超過光輸出更大的電流。

2003年9月，一個藍(lán)色的LED新類型，表明了公司Cree公司，公司提供24毫瓦在20 毫安 [毫安]。這產(chǎn)生了商業(yè)包裝的白光在20毫安給65流明/瓦，成為最亮的白光LED在商業(yè)上可利用的時間，超過4倍效率，標(biāo)準(zhǔn)白熾燈。2006年，他們表現(xiàn)出了創(chuàng)紀(jì)錄的白光LED 131流明/瓦的發(fā)光效率在20毫安的原型。此外，首爾半導(dǎo)體已計劃為135流明/ 2007流明和80 × 145 / W的2008年，這將更好地接近以上標(biāo)準(zhǔn)白熾燈和數(shù)量級的改善，甚至比標(biāo)準(zhǔn)的熒光燈。[30] 日亞化學(xué)公司已開發(fā)出白光LED 150流明的發(fā)光效率/ W于一正向電流為20毫安。

發(fā)光二極管

應(yīng)當(dāng)指出，高功率（≥1瓦）LED的普通照明應(yīng)用的實際需要。這些器件的典型工作電流開始在350毫安的電流。

請注意，這些效率只，在低溫實驗室舉行的LED芯片的。在照明應(yīng)用，工作在更高的溫度和驅(qū)動電路損耗，效率非常低。美國能源部（DOE）的白熾燈或節(jié)能燈測試的商業(yè)LED燈設(shè)計，以取代表明，平均療效仍有約46流明/ 2009年鎢（測試時的性能介于17流明/ W到79流明/瓦）。

克里2月3日發(fā)出的新聞稿，對2010年的實驗室原型在室溫下發(fā)光二極管實現(xiàn)每瓦208流明。在相關(guān)色溫?fù)?jù)報4579光

壽命和故障

主要文章： LED的失效模式列表

固態(tài)裝置，如LED是非常有限的受磨損，如果操作在低電流和低的溫度。在20世紀(jì)70年代和80年代生產(chǎn)的LED的許多服務(wù)至今。一生中引述的典型是25,000到100,000小時，但熱和當(dāng)前的設(shè)置可以延長或縮短這個時間顯著。

癥狀最常見的LED（和激光二極管）的失敗是效率逐漸降低光輸出和損失。突發(fā)故障，雖然罕見，也可能發(fā)生。早期的紅色LED值得注意的是他們的短壽命。隨著高功率LED發(fā)展的設(shè)備受到交界處的溫度較高，比傳統(tǒng)設(shè)備提高電流密度。這會導(dǎo)致壓力的物質(zhì)，可能導(dǎo)致早期退化的光輸出。為了定量分類的方式在一個標(biāo)準(zhǔn)化的一生已建議使用條款L75和L50的時間，這是一個給定的LED將達到75％和50％的光輸出分別。L50相當(dāng)于半生活中的LED。

像其他照明裝置，發(fā)光二極管性能的溫度依賴性。大多數(shù)制造商所公布的LED的評級為25 ° C的工作溫度用發(fā)光二極管信號燈戶外，如交通信號或-路面，而且是在那里的氣候利用燈具內(nèi)的溫度會非常熱，可能導(dǎo)致失敗，甚至低信號強度。

發(fā)光二極管保持一致，即使在寒冷的氣溫光輸出，與傳統(tǒng)的照明方法。因此，LED技術(shù)可能是一個很好的替代冰箱照明等領(lǐng)域的超市，而且會持續(xù)時間比其他技術(shù)。由于發(fā)光二極管不產(chǎn)生像白熾燈泡的熱量，它們是一個能源效率的技術(shù)，如使用冷凍機等應(yīng)

發(fā)光二極管

用。另一方面，因為他們不會帶來太多的熱量，冰和雪更冷了，可能就建立在LED燈具氣候。這是一個問題困擾著機場跑道的燈光，雖然做了一些研究，試圖開發(fā)散熱技術(shù)，以熱轉(zhuǎn)移到其他地區(qū)的燈具。

實際應(yīng)用

第一個商用的LED被普遍用作替代白熾燈和霓虹燈標(biāo)志燈，并在7段顯示器，第一次在昂貴的設(shè)備，如實驗室和電子測試設(shè)備，后來在這些設(shè)備的電視，收音機，電話，計算器，甚至手表（見名單信號應(yīng)用）。這些明亮的紅色發(fā)光二極管是不夠只在指標(biāo)的使用，因為光輸出是不夠的，照亮的區(qū)域。.后來，其他的顏色，也成為廣泛使用的器具和設(shè)備出現(xiàn)了。.隨著技術(shù)變得更加先進的LED材料，光輸出增加，同時保持了效率和可靠性，以一個可接受的水平。.本發(fā)明和輕發(fā)展的高功率白光LED燈用于照明（見名單照明應(yīng)用）。大多數(shù)的LED進行了輸出非常常見5毫米T1的?和3毫米T1的軟件包，但隨著權(quán)力，它已成為越來越有必要擺脫過多的熱量，以保持可靠性，所以更復(fù)雜的軟件包已被有效改編散熱。先進的軟件包為國家的設(shè)施，高功率LED承擔(dān)早期LED的相似性很小。

在低能耗，低維護和現(xiàn)代的LED小尺寸，導(dǎo)致顯示申請的狀況指標(biāo)和對各種設(shè)備和設(shè)施。大面積的LED顯示屏所用的球場為動態(tài)顯示和裝飾顯示器。薄，輕信息顯示用于機場和鐵路車站，列車的目的地為顯示，公共汽車，電車，輪渡。

單一顏色的光，能提供適合的交通燈和信號，出口標(biāo)志，應(yīng)急照明車，船舶燈籠和基于LED圣誕燈飾。在寒冷的氣候條件下，LED交通燈可能仍然積雪覆蓋。[86]紅色或黃色LED的使用和在環(huán)境中的字母數(shù)字顯示指標(biāo)在夜視必須保留：飛機駕駛艙，潛艇和船舶橋梁，天文觀測，并在該領(lǐng)域，如夜間動物觀賞和軍事領(lǐng)域的使用。

由于他們長期生活和快速開關(guān)時間，LED已經(jīng)被用于汽車的高安裝剎車燈，卡車和巴士剎車燈和轉(zhuǎn)向信號，對一些時間，但許多汽車現(xiàn)在使用的LED集群為他們的尾燈。LED的使用也有優(yōu)勢，因為LED的造型與能比白熾燈照明形成更薄更拋物線反射鏡。

發(fā)光二極管

在采取點亮（或許0.5秒比白熾燈泡快）提高了更多的時間給司機安全作出反應(yīng)的時間明顯改善。據(jù)報道，在正常的公路上行駛汽車的長度等于增加了汽車后面的反應(yīng)時間。白光LED頭燈也開始露面。在一個雙密度電路（即后方標(biāo)記和剎車），如果LED的脈沖頻率是不是一個足夠快的，他們可以創(chuàng)建一個幽靈陣列，其中LED的鬼形象將出現(xiàn)如果眼睛快速掃描整個陣列。

由于產(chǎn)量低的LED相對便宜，他們也用在應(yīng)用，如許多臨時glowsticks，throwies和光子紡織 Lumalive。藝術(shù)家們也可用于發(fā)光二極管的LED藝術(shù)。

天氣/全危害無線電接收器與特定地區(qū)郵件編碼（同）有3個LED：紅色的警告，手表橙，并發(fā)出黃色的警告時與發(fā)言。

照明

主要文章： LED燈

隨著高效率，高功率LED的發(fā)展已成為可能納入照明和照明的LED。更換燈泡已以及專用的固定裝置和LED燈。LED是作為街燈和其他建筑照明在使用變色。在機械強度，壽命長，是用于汽車照明在汽車，摩托車和自行車燈。

LED已經(jīng)被用于照明的街道和停車場。2007年，意大利村Torraca首先是轉(zhuǎn)換整個照明系統(tǒng)，發(fā)光二極管。

LED的使用日益普遍的水族館照明。特殊的珊瑚礁水族館，LED燈提供與減少熱量輸出效率的光源，以幫助保持最佳溫度水族館?；贚ED的水族館燈具也有被手動調(diào)節(jié)，以產(chǎn)生特定顏色的珊瑚，魚類理想的色彩頻譜的優(yōu)勢，和無脊椎動物，同時優(yōu)化photosynethically有效輻射（PAR）的增加，如珊瑚生長和光合生活的可持續(xù)性，?？?，蛤和海藻。這些裝置可以電子編程，以模擬在一天不同的照明條件，反映了太陽和月亮的分階段動態(tài)礁的經(jīng)驗。LED燈具的成本通常高達5倍，而同樣額定熒光燈或高強度放電照明礁水族館的設(shè)計，沒有高輸出的日期。

LED是現(xiàn)在也被用來在機場和直升機場照明。機場的LED燈具目前包括中等強度的跑道燈，跑道中心線燈照明和阻撓。

也適用于發(fā)光二極管背光的液晶電視和輕巧筆記本電腦顯示器和光來源的DLP投影機（見LED電視）。RGB LED的增加顏色的發(fā)光二極管

色域高達45％。顯示器屏幕電視和電腦，可使用越來越薄的LED背光的。

缺乏的紅外/熱輻射使理想用于LED 舞臺燈使用的RGB LED的銀行，可以輕松地改變傳統(tǒng)的舞臺燈光色彩，減少采暖，照明以及醫(yī)療在紅外輻射是有害的。

由于LED小，堅固耐用，幾乎無需電源，他們都是手工使用等裝置舉行手電筒。的LED 閃燈，或照相機閃光燈工作在一個安全，低電壓，相對于250 +伏特發(fā)現(xiàn)常見的氙氣閃光燈的照明。這一點尤其適用相機到移動電話，其中空間電路是十分寶貴和笨重的電壓增加，是不可取的。發(fā)光二極管用于照明的紅外夜視應(yīng)用，包括安全攝像機。LED的周圍環(huán)攝像機，一個旨在向，反光 的背景，使色度鍵控在影片制作。

LED是用于裝飾照明以及。用途包括但不限于室內(nèi)/室外裝飾，豪華轎車，貨物拖車，轉(zhuǎn)換車，游船，休閑車，船，汽車，卡車和公用事業(yè)。LED照明裝飾也可以進來的燈光公司標(biāo)志，并加強與在電影院和禮堂過道照明形式。

智能照明

光可以被用來傳輸寬帶數(shù)據(jù)，這已在實施的IrDA標(biāo)準(zhǔn)，使用紅外線發(fā)光二極管。由于LED可以循環(huán)和關(guān)閉每百萬第二次，他們可以在效應(yīng)，成為無線路由器的數(shù)據(jù)傳輸。[89] 激光也可調(diào)制這種方式。

可持續(xù)照明

高效照明需要可持續(xù)建筑。一個13 30w的LED燈泡生產(chǎn)450到650 流明 [90]。這相當(dāng)于一個標(biāo)準(zhǔn)的40瓦白熾燈泡[91]。一個標(biāo)準(zhǔn)的40瓦白熾燈泡有一個預(yù)期壽命1000小時，而LED的可以繼續(xù)經(jīng)營效率與減少超過50,000小時，50倍的白熾燈泡長。

環(huán)保選擇

單千瓦小時的電力將產(chǎn)生1.34磅（610 g）款二氧化碳排放量。[92]假設(shè)平均燈泡是一天10小時，一個40瓦的白熾燈泡會產(chǎn)生196磅（89公斤）每年的二氧化碳。13瓦的LED相當(dāng)于將只負(fù)責(zé)跨度為6300磅（29千克）的 CO 2比同一時間。建筑物的碳足跡，從照明，可降低68％，通過交換在氣候溫暖的新型LED所有白熾燈泡。在寒冷的氣候，能源節(jié)約可能較低，因為將需要更多的發(fā)光二極管

供暖，以彌補較低的溫度。

發(fā)光二極管也非又名毒性不像更受歡迎節(jié)能燈泡選項：緊湊型熒光燈緊湊型熒光燈含有有害的痕跡汞。雖然在一個緊湊型熒光燈小，引入環(huán)境少即是最好的汞量。

經(jīng)濟可持續(xù)發(fā)展

LED燈泡的照明可能是因為他們的壽命很長的家庭或辦公空間成本效益的選擇。消費者使用的LED作為一種替代傳統(tǒng)的照明系統(tǒng)是目前妨礙了高成本和低效率的可用產(chǎn)品。測試結(jié)果表明：2009年美國能源部35流明的平均療效/瓦，低于典型的節(jié)能燈，和低至9流明/瓦，比標(biāo)準(zhǔn)的白熾燈泡壞。[90] LED燈泡的初始成本高的商業(yè)是由于昂貴的藍(lán)寶石 基板是生產(chǎn)過程的關(guān)鍵。藍(lán)寶石器具必須再加上鏡子一樣反射光線收集器，否則將被浪費。

2008年，材料科學(xué)的研究小組在美國普渡大學(xué)成功地在藍(lán)寶石元件LED燈泡生產(chǎn)用的替代品。[93]。該小組使用的金屬涂層的硅晶片的一個內(nèi)置的反射層，氮化鋯，以減少LED的整體生產(chǎn)成本。他們預(yù)測，在未來數(shù)年內(nèi)，LED的革命，新技術(shù)生產(chǎn)的節(jié)能燈將具有競爭力的價格。較便宜的LED將不僅是最好的節(jié)能器，但也是一個非常經(jīng)濟的燈泡。

非視覺應(yīng)用

光有許多其他用途除了用于看。LED是用于這些應(yīng)用程序。在三組的用途秋季：通訊，傳感器和光物質(zhì)的相互作用。

這些LED燈由可調(diào)制很快使他們在廣泛用于光纖和自由空間光通信。這包括遠(yuǎn)程控制。，如電視機和錄像機，其中紅外發(fā)光二極管通常使用光電絕緣器使用一個LED一結(jié)合光電二極管或光電晶體管兩個電路之間提供電氣隔離的一個信號通道的。這是特別有用的電壓低的地方在醫(yī)療設(shè)備的信號從一個傳感器電路（通常是電池供電的接觸）與一個活的有機體，必須是電動操作隔離任何可能的電氣故障監(jiān)控裝置在錄音或有潛在危險的電壓。一個光隔離器還允許資料傳輸電路之間不共享一個共同的地電位。

許多傳感器系統(tǒng)依賴于光作為信號源。LED通常理想作為光源，由于該傳感器的要求。LED被用來作為移動傳感器，例如在光學(xué)計算機鼠標(biāo)。任天堂的Wii的傳感器使用紅外線LED酒吧。

發(fā)光二極管

在脈搏血氧計測量氧飽和度。一些典型的平板掃描儀的使用，而不是數(shù)組的RGB LED的冷陰極熒光燈作為光源。發(fā)光顏色有三個獨立的控制允許掃描儀校準(zhǔn)更精確的色彩平衡本身，也沒有必要熱身。此外，它的傳感器只需要是單色的，因為在頁掃描被任何一時間點只能根據(jù)的是由一個單一顏色點燃。觸摸感應(yīng) ：由于LED也可作為用于光電二極管，它們既可以用于發(fā)射照片和檢測。這可用于，例如觸摸感應(yīng)屏幕，從光線反射或注冊一個手指觸摸筆。

許多材料和生物系統(tǒng)是敏感的，或依賴于光。拓展燈用發(fā)光二極管，以增加光合作用的植物，細(xì)菌和病毒可以使用去除水中的其他物質(zhì)和紫外線 LED的消毒。其他用途的紫外線固化油墨的一些設(shè)備和涂料的應(yīng)用，以及打印機的LED。

LED的使用，特別是有趣的植物修煉，這主要是因為它更節(jié)省能源，減少熱量產(chǎn)生（可損害植物接近熱燈），并能提供最佳的植物生長和開花期比目前使用的光的頻率增加至燈： 海港巡邏組（高壓鈉），氫（金屬鹵化物）或節(jié)能燈 /低能量。但它不取代這些增長燈由于它具有較高的零售價格，為大規(guī)模生產(chǎn)和LED產(chǎn)品的開發(fā)工具包將變得更加便宜。

發(fā)光二極管也被用來作為一種媒介，質(zhì)量電壓參考的電子線路。正向電壓降（例如，約1.7 V的一個正常的LED紅色）可以用來代替齊納二極管在低電壓穩(wěn)壓器。紅色發(fā)光二極管具有平坦的我/視頻膝蓋以上的曲線;氮化物基發(fā)光二極管具有相當(dāng)陡峭的I / V曲線，不應(yīng)用有助于這一點。雖然LED正向電壓電流更比一個好齊納依賴，齊納二極管的電壓并不普遍低于現(xiàn)有約3五

光來源

機器視覺系統(tǒng)通常需要明亮，均勻的照明，使感興趣的特征更容易處理。LED通常用于這一目的，這是應(yīng)用領(lǐng)域的可能仍然地區(qū)之一，主要應(yīng)用到足夠低的價格下降，使信號及照明應(yīng)用更廣泛。條碼掃描儀是機器視覺最常見的例子，很多便宜的，而不是用紅色發(fā)光二極管激光器。發(fā)光二極管構(gòu)成的理想光源近的機器視覺系統(tǒng)有幾個原因：

在照明領(lǐng)域的規(guī)模通常比較小，機器視覺系統(tǒng)往往相當(dāng)昂貴，因此，光源的成本通常是輕微的關(guān)注。但是，它可能不容易更換光源在復(fù)雜破碎機械的人選，而在這里，LED的使用壽命長，是一

發(fā)光二極管

個好處。

發(fā)光二極管的元素往往是小，可與平地，甚至形基板（多氯聯(lián)苯等），使明亮，均勻的來源可以設(shè)計出直射光檢查，嚴(yán)格控制對高密度零件放置方向。通?？梢缘玫叫。瑑r格低廉鏡頭和擴散，幫助實現(xiàn)超過照明均勻性的控制水平和高光密度。LED光源可以在多種配置型（用于反射照明射燈;環(huán)同軸照明燈，輪廓燈照明回來;線性組合，平面，大尺寸面板，為彌漫性，全方位的照明圓頂來源）。

LED可以很容易地選通（在微秒范圍及以下），并與影像同步。高功率LED，可讓即使很短的光脈沖明亮的圖像。這是經(jīng)常使用，以獲得清晰和銳利“仍然是”快速移動的部分圖像。

發(fā)光二極管有幾種不同的顏色和波長，容易允許使用每個應(yīng)用程序，不同的顏色可能會提供更好的利益特征能見度最好的顏色。擁有一個精確已知的頻譜可以緊密配合，以用于分隔帶寬或信息，以減少環(huán)境光干擾的影響過濾器。發(fā)光二極管通常工作在較低溫度下工作，簡化管理和熱耗散，因此允許塑料鏡片，過濾器和擴散器使用。防水單位也可以輕易地被設(shè)計為在惡劣或潮濕的環(huán)境（允許使用的食品，飲料，石油工業(yè)）。

第二篇：實驗三 低頻功率放大器

實驗三

低頻功率放大器——OTL功率放大器

（即原資料的實驗十六）

一、實驗?zāi)康?/p>

1、進一步理解OTL功率放大器的工作原理。

2、加深理解OTL電路靜態(tài)工作點的調(diào)整方法。

3、學(xué)會OTL電路調(diào)試及主要性能指標(biāo)的測試方法。

二、實驗儀器

1、雙蹤示波器

2、萬用表

3、毫伏表

4、直流毫安表

5、信號發(fā)生器

三、實驗原理

圖16-1 OTL功率放大器實驗電路

圖16-1所示為OTL低頻功率放大器。其中由晶體三極管T1組成推動級（也稱前置放大級），T2、T3是一對參數(shù)對稱的NPN和PNP型晶體三極管，它們組成互補推挽OTL功放電路。由于每一個管子都接成射極輸出器形式，因此具有輸出電阻低，負(fù)載能力強等優(yōu)點，T1管工作于甲類狀態(tài)，適合于作功率輸出級。它的集電極電流IC1由電位器RW1進行調(diào)節(jié)。IC1的一部分流經(jīng)電位器RW2及二極管D，給T2、T3提供偏壓。調(diào)節(jié)RW2，可以使T2、T3得到合適的靜態(tài)電流而工作于甲、乙類狀態(tài)，以克服交越失真。靜態(tài)時要求輸出端中點A的電位UA?1UCC，可以通過調(diào)節(jié)RW1來實現(xiàn)，又由于RW1的一端接在A點，因此在2電路中引入交、直流電壓并聯(lián)負(fù)反饋，一方面能夠穩(wěn)定放大器的靜態(tài)工作點，同時也改善了非線性失真。

當(dāng)輸入正弦交流信號Ui時，經(jīng)T1放大、倒相后同時作用于T2、T3的基極，Ui的負(fù)半周使T2管導(dǎo)通（T3管截止），有電流通過負(fù)載RL（用嗽叭作為負(fù)載RL，嗽叭接線如下：

只要把輸出Uo用連接線連接到插孔LMTP即可），同時向電容C0充電，在Ui的正半周，T3導(dǎo)通（T2截止），則已充好電的電容器C0起著電源的作用，通過負(fù)載RL放電，這樣在RL上就得到完整的正弦波。

C2和R構(gòu)成自舉電路，用于提高輸出電壓正半周的幅度，以得到大的動態(tài)范圍。由于信號源輸出阻抗不同，輸入信號源受OTL功率放大電路的輸入阻抗影響而可能失真，R0作為失真時的輸入匹配電阻。調(diào)節(jié)電位器RW2時影響到靜態(tài)工作點A點的電位，故調(diào)節(jié)靜態(tài)工作點采用動態(tài)調(diào)節(jié)方法。為了得到盡可能大的輸出功率，晶體管一般工作在接近臨界參數(shù)的狀態(tài)，如ICM，U（BR）CEO和PCM，這樣工作時晶體管極易發(fā)熱，有條件的話晶體管有時還要采用散熱措施，由于三極管參數(shù)易受溫度影響，在溫度變化的情況下三極管的靜態(tài)工作點也跟隨著變化，這樣定量分析電路時所測數(shù)據(jù)存在一定的誤差，我們用動態(tài)調(diào)節(jié)方法來調(diào)節(jié)靜態(tài)工作點，受三極管對溫度的敏感性影響所測電路電流是個變化量，我們盡量在變化緩慢時讀數(shù)作為定量分析的數(shù)據(jù)來減小誤差?！鵒TL電路的主要性能指標(biāo)：

1、最大不失真輸出功率Pom

21UCC理想情況下Pom?，在實驗中可通過測量RL兩端的電壓有效值，來求得實際的

8RL2U0

Pom?

（16-1）

RL2、效率η

??Pom?100%

（16-2）PEPE—直流電源供給的平均功率

理想情況下ηmax＝78.5%。在實驗中，可測量電源供給的平均電流Idc（多測幾次I取其平均值），從而求得

PE?UCC?Idc（16-3）

負(fù)載上的交流功率已用上述方法求出，因而也就可以計算實際效率了。

四、實驗內(nèi)容

1、關(guān)閉系統(tǒng)電源。按圖16-1正確連接實驗電路。

2、用動態(tài)調(diào)試法調(diào)節(jié)靜態(tài)工作點，先使RW2＝0，Us接地。

3、打開系統(tǒng)電源，用萬用表測量Ａ點（即LTP2）電位，調(diào)節(jié)電位器RW1，使UA?

4、關(guān)閉系統(tǒng)電源。斷開US接地線，連接信號源輸出和US。

5、打開系統(tǒng)電源。調(diào)節(jié)信號源輸出f=1KHz、峰峰值為50mV的正弦信號作為Us，逐漸加大輸入信號的幅值，用示波器觀察輸出波形，此時，輸出波形有可能出現(xiàn)交越失真（注意：沒有飽和和截止失真）

6、緩慢增大RW2，由于RW2調(diào)節(jié)影響A點電位，故需調(diào)節(jié)RW1，使UA?1UCC。21UCC（在2Us=0的情況下測量）。從減小交越失真角度而言，應(yīng)適當(dāng)加大輸出極靜態(tài)電流IC2及IC3，但該電流過大，會使效率降低，所以通過調(diào)節(jié)RW2一般以50mA左右為宜（即測量LTP4和LTP2，或LTP6和LTP2之間的電壓為110mV左右為宜)。注意：

①在調(diào)整RW2時，一是要注意旋轉(zhuǎn)方向，不要調(diào)得過大，更不能開路，以免損壞輸出管。

②輸出管靜態(tài)電流調(diào)好，如無特殊情況，不得隨意旋動RW2的位置。

測量最大輸出功率Pom

1、按上述的實驗步驟調(diào)節(jié)好功率放大電路的靜態(tài)工作點。

2、關(guān)閉系統(tǒng)電源。連接信號源輸出和US。輸出端接上嗽叭即RL。

3、打開系統(tǒng)電源。調(diào)節(jié)信號源輸出f=1KHz、30mV的正弦信號Ｕs，用示波器觀察輸出電壓ＵO波形。逐漸增大Ui，使輸出電壓達到最大不失真輸出，通過觀察示波器得到Uom的峰峰值，再用公式Uom?Uom峰峰值求出Uom的有效值，用萬用表的歐姆檔測出RL的22阻值，最后下面公式計算出Pom。

2Uom

Pom?

RL注意：萬用表的歐姆檔測出RL的阻值的時候，關(guān)閉系統(tǒng)電源，斷開電路連線。

五、實驗數(shù)據(jù)

六、問題與結(jié)論

1、為何OTL電路會出現(xiàn)交越失真？

第三篇：低頻功率放大器課程設(shè)計報告

《電路與模擬電子技術(shù)》

課程設(shè)計報告

低頻功率放大器

一、摘要

低頻功率放大器的主要應(yīng)用是對音頻信號進行功率放大，本文介紹了具有弱信號放大能力的低頻功率放大器的基本原理、內(nèi)容、技術(shù)路線。整個電路主要分為穩(wěn)壓電源、前置放大器、功率放大器、波形變換電路共4 部分。穩(wěn)壓電源主要是為前置放大器、功率放大器提供穩(wěn)定的直流電源。前置放大器主要是實現(xiàn)電壓的放大。功率放大器實現(xiàn)電流、電壓的放大。波形變換電路是將正弦信號變換成規(guī)定要求的方波信號。設(shè)計的電路結(jié)構(gòu)簡潔、實用，充分利用到了集成功放的優(yōu)良性能。實驗結(jié)果表明該功率放大器在帶寬、失真度、效率等方面具有較好的指標(biāo)、較高的實用性,為功率放大器的設(shè)計提供了廣闊的思路。

二、關(guān)鍵字

前置放大級電路

功率放大

穩(wěn)壓電源電路

波轉(zhuǎn)換電路

三、總體設(shè)計方案論證及選擇

根據(jù)課設(shè)要求, 我們所設(shè)計的低頻功率放大器應(yīng)由以下幾個部分組成：穩(wěn)壓電路、前置放大、功率放大以及波形變換電路。下面對每個單元電路分別進行論證：

前置放大級：

設(shè)計要求前置放大輸入交流接到地時，RL=8?的電阻負(fù)載上的交流噪聲功率低于10mw因此要選用低噪音運放。本裝置選用的優(yōu)質(zhì)低噪音運放NE5532AI。設(shè)計要求輸入電壓幅度為5~700mV時，輸出都能以Po≥10W滿功率不失真輸出，信號需放大幾千倍，有考慮到運放的放大倍數(shù)與通頻帶的關(guān)系，故采用兩級放大，增益調(diào)節(jié)可用電位器手動調(diào)節(jié)，也可用自動增益控制，但考慮到題目中的“使用”倆字（例如輸入信號不是正弦信號，而是大動態(tài)音樂信號），本裝置采用手動增益調(diào)節(jié)。

功率放大級：

根據(jù)設(shè)計題目要求，在供原則的功率放大可由分立元件組成，也可由集成電路完成。由分立元件組成的功放，如果電路選擇好，參數(shù)恰當(dāng)，元件性能優(yōu)越，且制作和調(diào)試的號，則性能很可能高過較好的集成功效。許多優(yōu)質(zhì)功放是分立功放。但其中有一個元件出現(xiàn)問題或是搭配不當(dāng)，則性能很可能低于一般集成功放，為了不至于因過載，過流，過熱等損壞還得加復(fù)雜的保護電路。

現(xiàn)在市場上也有很多性能優(yōu)越的集成功放芯片，如TDA2040A,LM1875，TDA1514等。集成功放具有工作可靠，外圍電路簡單，保護功能較完善，易制作易調(diào)試等特點，雖不及頂級功放的性能，但滿足并超過本設(shè)計的要求問題的。

綜上所述，考慮時間緊，在滿足要求的前提下，選擇易調(diào)試的集成功放。

我們熟悉的集成功放有TDA2040A，LM1875，TDA1514等，其中TDA2040A功率量不大，TDA1514外圍電路較復(fù)雜，且易自激。這兩種功放的低頻率特征都欠佳，LM1875外圍電路簡單，電路熟悉，低頻特性好，保護功能齊全。它的不足之處是高頻特性較差（BW<=70KHz），但對于本設(shè)計要求的50Hz~10KHz已足夠，因此選用LM1875作功放。

波形變換電路：

直接采用施密特觸發(fā)器進行變換與整形。而施密特電路可用高精度、高速運算電路搭接而成，也可采用專用施密特觸發(fā)器構(gòu)成，還可以選用NE5532P電路構(gòu)成。

通過比較，本課程設(shè)計中施密特電路采用高精度、高速運算放大器LF357構(gòu)成。

自制穩(wěn)壓電源：

本系統(tǒng)設(shè)計采用三端集成穩(wěn)壓電源電路，選用LM7815、LM7915三端集成穩(wěn)壓器。

四、設(shè)計方案的原理框圖

圖1 總體設(shè)計

放大通道正弦信號外供正弦信號源弱信號前置放大級變換電路正、負(fù)極性對稱方波 自制直流穩(wěn)壓電源功率放大級RL=8Ω~220V50Hz

五、總體電路圖、接線圖及說明 XFG101C210uF2V318 V 683XDA1THDU2A1C458U3B710uF9R5850%050kΩKey=AXSC1Ext Trig+_A+_B+_10NE5532AI746R21MΩ0R415kΩR31kΩ4C347uF0R61MΩ14110R71kΩ12C547uF004NE5532AIR822kΩR9V4-18 V 1350%050kΩKey=A150

圖2 前置放大電路

說明：前置放大由兩級NE5532典型應(yīng)用電路組成，各級均采用固定增益輸出衰減組成。要求當(dāng)各級輸出不衰減，輸入Vp=5mV時，輸出Va.pp>=2.53V。

0V218 V 5XFG1514C5220uFU10C3100nFD11N400797+XSC1Ext Trig+_A_+B_8C710uF3R1100kΩ023LM1875T2R320kΩ6V1-18 V 0C2220uF0C4100nF0R21kΩ4D21N4007R48Ω10C6210uF0C147uF0

圖3 功率放大電路

說明：功率放大器選擇用集成功放LM1875，采用典型電路，此電路中R3，R2組成反饋網(wǎng)絡(luò)，C1為直流反饋電容，R1為輸入接地電阻，防止輸入電路時引入感應(yīng)噪聲，C7為信號耦合電容，D1，D2為保護二極管，R4和C6組成退偶電路，防止功放產(chǎn)生高頻自激，C5，C2，C3，C4是電源退耦電容。

六、主要元器件選擇

1）穩(wěn)壓電路中選用LM7815、LM7915三端集成穩(wěn)壓器

2）因為LF357屬于FET管，具有良好的匹配性能，輸入阻抗高、低噪聲、漂移小、頻帶寬、響應(yīng)快等特點，所以在正弦波一方波轉(zhuǎn)換電路中采用集成運放LF357

3）在前置放大級電路中采用集成雙運放NE5532,在功率放大級中采用運放LM1875。

七、電路參數(shù)計算

前置放大計算

對于第一級放大，要求在信號最強時，輸出不失真，即Vp=700mV時，輸出Vom<11V(低于電源電壓1V)。所以

A1=Vom/Vp=11/0.7 =15.7 取A1=15.當(dāng)輸入信號最小，即Vpp=10mV，而輸出不衰減時

V01.pp=A1*Vi.pp=15*10=150mA 第二級放大要求輸出V02.pp>2.53V,考慮到元件誤差的影響，取V02.pp=3V，而輸入信號最小為150mV，則第二級放大倍數(shù)是

A2 = V02.pp/ V01.pp=20 功率放大計算：

LM1875開環(huán)增益為26dB，即放大倍數(shù) A=20

因為要求輸出到8Ω電阻負(fù)載上的功率P0>10 W。而 Vom=2Rl*P。=12.65V 加上功率管管壓降2V，則

V=Vom=12.65+2=14.65V 取電源電壓為15V

Icm=2P。*Rl=1.518A PV =2V * Icm/? =15.1W

八、Multisim仿真結(jié)果

前置放大

直流穩(wěn)壓

功率放大

波形轉(zhuǎn)換

九、收獲與體會

通過此次課程設(shè)計鍛煉，我不僅深深體會到理論知識與實踐結(jié)合的不易，還深入了解并學(xué)會了一種簡單實用、成本低的低頻功率放大器的電路設(shè)計方法。課設(shè)過程中為了讓自己的設(shè)計更加完善，更加符合工藝標(biāo)準(zhǔn)，一次次翻閱熱處理方面的書籍是十分必要的，同時也是必不可少的。通過這次課程設(shè)計我也發(fā)現(xiàn)了自身存在的不足之處，雖然感覺理論上已經(jīng)掌握，但在運用到實踐的過程中仍有意想不到的困惑，經(jīng)過一番努力才得以解決。我懂得了學(xué)習(xí)的重要性，了解到理論知識與實踐相結(jié)合的重要意義。

十、參考文獻

[1] 胡翔駿 電路分析(第二版)北京：高等教育出版社 2007 [2] 華成英、童詩白 模擬電子學(xué)基礎(chǔ)（第四版）北京：高等教育出版社 2006 [3] 黃智偉 全國大學(xué)生電子設(shè)計競賽系統(tǒng)設(shè)計 北京：北京航空航天大學(xué)出版社 2006 [4] 夏路易、石宗義 電路原理圖與電路板設(shè)計教程 北京希望電子出版社 2002 [5] 谷麗華、辛?xí)詫帯⒚葱駯| 實用低頻功率放大器的設(shè)計 沈陽化工學(xué)院學(xué)報 [6] 高玉良 電路與模擬電子技術(shù) 北京高等教育出版社

十一、附件

XSC3V120 Vrms 60 Hz 0° A+_BExt Trig+_+_D91N5402U1LM7815CTC7330nF5C810uFD11N5402D31N5402D21N5402D4C11N5402100nF03R1C31kΩ2.2mFC22.2mF0IC=35VIC=35VXSC1Ext Trig+D51N5402D71N54028D6+_A_B+_91N5402D8C41N5402100nFR21kΩC5D1001N5402C6132.2mFIC=35VU2LM7915CT002.2mFIC=35VXSC2Ext Trig+_11C1010uFC9330nF00A+_+B_0 圖2

直流穩(wěn)壓電路

說明：直流穩(wěn)壓電源部分為整個功放電路提供能量，根據(jù)設(shè)計的前置放大級電路和功率放大級電路的要求，僅需要穩(wěn)壓電源輸出的一種直流電壓即+15V。因三端穩(wěn)壓器具有結(jié)構(gòu)簡單、外圍元器件少、性能優(yōu)良、調(diào)試方便等顯著優(yōu)點，故本設(shè)計中采用三端穩(wěn)壓電路。兩組獨立的20V交流，經(jīng)過橋堆整流，大電容濾波，再加0.1uF小電容濾掉電源中的高頻分量?？紤]到制作過程中電源空載時的電容放電可在輸出電容并上1K大功率電阻。另外還要給7815，7915來獲得+15V、萬一輸入端短路，大電容放電會使穩(wěn)壓塊由于反電流沖擊而損壞，加兩個二極管可使反相電流流向輸入端起保護作用。

V260V140XSC11R410kΩ2D21N4728A5R510kΩR6831Ext Trig+3C1818 V U1A330nF1824NE5532PV370C2-18 V 330nFU2A+_AB_+_R310kΩ700mVrms 1000 Hz 0° 30924NE5532P1kΩD1Key=A1N4728A050% 圖5 波形變換電路（NE5532P）

說明：將1KHZ的正弦波變?yōu)橥l率的對稱方波。因LF357屬于FET管，具有良好的匹配性能，輸入阻抗高、低噪聲、漂移小、頻帶寬、響應(yīng)快等特點，所以本課程設(shè)計中施密特電路采用高精度、高速運算放大器LF357構(gòu)成，而NE5532運放做隔離用。

第四篇：低頻功率放大器概述

第4章 低頻功率放大器

【課題】

4.1低頻功率放大器概述

【教學(xué)目的】

1．了解低頻功率放大器基本要求。2．掌握功率放大器的三種工作狀態(tài)。3．了解功率放大器的常用耦合方式?！窘虒W(xué)重點】

1．低頻功率放大器基本要求。2．低頻功率放大器的分類?！窘虒W(xué)難點】

1．低頻功率放大器基本要求。2．功率放大器的三種工作狀態(tài)?！窘虒W(xué)參考學(xué)時】

1學(xué)時 【教學(xué)方法】

講授法 【教學(xué)過程】

一、引入新課

1．復(fù)習(xí)電壓放大器主要任務(wù)。

2．列舉低頻功率放大器的應(yīng)用：如擴音系統(tǒng)或收音機電路中的功放電路。

二、講授新課

4.1.1低頻功率放大電路的基本要求

功率放大器作為放大電路的輸出級, 具有以下幾個特點和基本要求： 1．能向負(fù)載輸出足夠大的不失真功率

由于功率放大器的主要任務(wù)是向負(fù)載提供不失真的信號功率，因此，功率放大器應(yīng)有較高的功率增益，即應(yīng)有較高的輸出電壓和較大的輸出電流。

2．有盡可能高的能量轉(zhuǎn)換效率

功率放大器實質(zhì)上是一個能量轉(zhuǎn)換器，它將電源供給的直流能量轉(zhuǎn)換成交流信號的能量輸送給負(fù)載，因此，要求其轉(zhuǎn)換效率高。

3．盡可能小的非線性失真

由于輸出信號幅度要求較大，功放管（三極管）大都工作在飽和區(qū)與截止區(qū)的邊沿，因此，要求功放管的極限參數(shù)ICm、PCm、V（BR）CEO等除應(yīng)滿足電路正常工作外還要留有一定余量，以減小非線性失真。4．功放管散熱性能要好

直流電源供給的功率除了一部分變成有用的信號功率以外，還有一部分通過功放管以熱的形式散發(fā)出去（管耗），因此，降低結(jié)溫是功率放大器要解決的一個重要問題。4.1.2低頻功率放大器的分類

1．按電路工作狀態(tài)分類（1）甲類功放電路

甲類功放電路中的功放管始終工作在三極管輸出特性曲線的線性部分如圖4.1（a）所示，即在輸入信號的整個周期內(nèi)，功放管始終導(dǎo)通，故電路輸出波形失真小，但因靜態(tài)時，功放管處于導(dǎo)通狀態(tài)，且靜態(tài)電流（ICQ）較大，電路轉(zhuǎn)換效率較低，理想情況下最大效率達50%。

（2）乙類功放電路

乙類功放電路在靜態(tài)時，功放管處于截止?fàn)顟B(tài)，如圖4.1（b）所示，即在輸入信號的整個周期內(nèi)，功放管只在輸入信號的半個周期內(nèi)導(dǎo)通的。因此，電路需用兩只參數(shù)基本一致的功放管輪流工作（推挽）才能輸出完整的波形信號。由于靜態(tài)電流為零，電路轉(zhuǎn)換效率較高，理想情況下可達78.5%，但因電路輸出波形存在交越失真（注：該內(nèi)容將在4.2 常用低頻功率放大器中學(xué)習(xí)），需解決失真問題。

（3）甲乙類功放電路

甲乙類功放電路在靜態(tài)時，功放管處于微導(dǎo)通狀態(tài)，如圖

4.1（c）所示，即在輸入信號的整個周期內(nèi)，功放管只在輸入信號的大半個周期內(nèi)導(dǎo)通。與乙類功率放大器電路一樣，需用兩只參數(shù)基本一致的功放管輪流工作（推挽）才能輸出完整的波形信號。由于靜態(tài)時管子仍然處于導(dǎo)通狀態(tài)，因此，在輸入信號很小時，兩個功放管同時都工作，克服了交越失真。電路轉(zhuǎn)換效率略低于乙類，原因是靜態(tài)時電路中仍有很小的電流，電路會消耗部分電源功率。

圖4.1 功放管的三種工作狀態(tài) 2．按耦合方式分類

（1）阻容耦合功放電路——功放電路輸出端通過耦合電容連接負(fù)載，如：OTL功放電路。（2）變壓器耦合功放電路——功放電路輸出端通過變壓器連接負(fù)載。變壓器具有阻抗變換作用，可使負(fù)載獲得最大功率，但由于有變壓器體積大、損耗大、頻率特性差等不足之處，目前應(yīng)用不多。

（3）直接耦合功放電路——功放電路輸出端無需通過任何元件而直接與負(fù)載相連，如：OCL功放電 路及集成功放電路。

三、課堂小結(jié)

1．低頻功放電路的基本要求。2．低頻功放電路的分類。

四、課堂思考

P97思考與練習(xí)題1、2、3。

五、課后練習(xí)

P108

一、填空題：1~4；

二、判斷題：2；

三、選擇題：1~4。

第五篇：專業(yè)英語低頻功率放大器翻譯

低頻功率放大器（G題）

湖北師范學(xué)院 吳 龍 霍姣姣 許成龍

賽前輔導(dǎo)教師：彭 琦 周兆豐 田開坤 曹庭水 文稿輔導(dǎo)教師:侯向鋒 張學(xué)文

摘要：本設(shè)計主要由低噪聲放大電路、帶阻濾波電路、信號放大電路、功率放大電路、峰值檢波電路、單片機控制、AD轉(zhuǎn)換、LCD顯示、穩(wěn)壓電源等電路組成。低噪聲放大電路選取甚低噪聲寬帶高精度運算放大器OP37，并采用并聯(lián)負(fù)反饋結(jié)構(gòu)，具有良好的抗共模干擾能力。帶阻濾波器在50Hz頻率點輸出功率衰減≥6dB，阻帶頻率范圍為43～57Hz，有效濾除了工頻噪聲的干擾。功率放大電路采用的是雙MOS晶體管的甲乙類推挽放大電路。設(shè)計的低頻功率放大器的通頻帶為6Hz～150kHz，很好地完成了通頻帶的擴展。該設(shè)計采用的電路結(jié)構(gòu)簡單，選取的器件價格便宜。測試結(jié)果表明，該低頻功率放大器可以很好地實現(xiàn)對低頻信號的放大作用，具有較高的實用性，其輸出帶寬、功率、效率等都達到了較高的指標(biāo)，為低頻功率放大器的設(shè)計提供了廣闊的思路。關(guān)鍵詞：功率放大器、OP37、MOS晶體管、輸出功率

Low frequency power amplifier(G)Hubei Normal University Wu dragon Huo Jiaojiao Xu Chenglong Pre-game counseling teachers: Peng Qi Zhou Zhaofeng Tian Kaikun Cao Tingshui presentation counseling teacher : Hou Xiangfeng Zhang Xuewen Abstract: mainly by the design of the low noise amplifier circuit, filter circuit, a signal amplifying circuit, a power amplification circuit, a peak detection circuit, SCM control, AD conversion, LCD display, regulated power supply circuit.Low noise amplifier circuit selection very low noise wideband high precision operational amplifier OP37, and the use of parallel negative feedback structure, with good anti interference capability.Band stop filter in50Hz frequency point output power attenuation was more than 6dB, the stopband frequencies in the range of 43~ 57Hz, effectively filtering the power frequency interference 1

noise.Power amplifying circuit using the double MOS transistor class AB push-pull amplifier circuit.Design of low-frequency power amplifier passband is 6Hz ~150kHz, done a good bandwidth expansion.The design adopts the circuit structure is simple, the selected device cheap.The test results show that, the low frequency power amplifier can realize the on the low frequency signal amplifying function, with high practicality, its output bandwidth, power, efficiency of all reached a high index, for low frequency power amplifier design provides a broad thinking.Key words: power amplifier, OP37, MOS, output power transistor