电子信息工程3_低频功率放大器(英文翻译)_2010.5.30

第一篇：电子信息工程3_低频功率放大器(英文翻译)_2010.5.30

大连理工大学城市学院

本科生毕业设计（论文）

外文翻译

学 院：电子与自动化学院 专 业： 电子信息工程 学 生： 丁 琳 指导教师： 马 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 T1¾ 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.发光二极管

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，发光二极管

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.发光二极管

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).发光二极管

发现和早期设备

电致发光被发现于1907年由英国实验者黄建忠回合的马可尼实

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验室，使用的晶体硅碳化物和急先锋，晶须探测器。俄罗斯奥列格罗维奇洛谢夫独立报上创造的1 27年的LED英寸他的研究主要分布在俄罗斯，德国和英国的科学杂志，但没有实际使用是由几个20年发现的。鲁宾Braunstein在美国广播公司报道红外排放砷化镓（砷化镓）及其他半导体合金在1955年。Braunstein观察红外发射二极管产生的使用结构简单的锑化镓（GaSb等），砷化镓，磷化铟（磷化铟）和硅锗（SiGe）的室内温度合金并在77开尔文。

1961年，实验者和加里罗伯特皮特曼Biard在工作德州仪器，发现，砷化镓红外辐射时发出的电流应用于红外发光二极管，并获得专利的。

第一个实际可见光谱（红色）发光二极管开发于1962年由尼克Holonyak小，而在工作通用电气公司。Holonyak是“发光二极管被视为”父亲的光。乔治克拉福德，学生毕业前的Holonyak，发明了第一个黄色的LED和改善。亮度红色的一个因素和红色LED橙10在1972年1976年，总磷皮尔索尔创造了第一个高亮度，光纤波长高效率发光二极管的发明新的电信传输半导体材料特别适合于光纤。

截至到1968年的可见光和红外发光二极管都非常昂贵，在美国以每单位200元，所以没有什么实际应用。的孟山都公司是第一个组织批量生产可见光LED，用磷化1968年砷化镓红色发光二极管生产适合指标。惠普（惠普）介绍了LED在1968年，最初使用砷化镓孟山都公司提供的。这项技术被证明有字母数字显示器的主要应用，并成为惠普的早期综合手持计算器。在20世纪70年代商业成功的LED器件在每个5岁以下被飞兆半导体光电产品美分。这些器件采用飞兆半导体在赫尔尼化合物半导体芯片，让工艺制造的平面博士发明的。的技术相结合的平面处理芯片制造和创新的封装使得飞兆半导体在率领球队光电先驱托马斯勃兰特实现所需费用减少。这些技术仍然是生产者使用的LED

持续发展

第一个高亮度蓝色发光二极管被证明中村修二的日亚化学公司，发光二极管

并于基于氮化铟镓的借贷关键发展对氮化镓在蓝宝石衬底上成核和发展了P的示范型氮化镓掺杂其中赤崎勇和H.天野在名古屋。1995年，阿尔贝托巴比在加的夫大学的实验室（GB）的调查的效率和可靠性的LED高亮度，表现出了非常令人印象深刻的联系结果通过使用透明的铟锡氧化物（ITO）薄膜上（磷化铝镓铟/砷化镓）的LED。蓝色发光二极管存在的，高效率LED的迅速发展导致了第一次的白光LED，它采用的 Y 三基地5 Ø 12：铈，或“ YAG激光 “，荧光粉涂层混合下变换）轻型蓝黄（生产出现白色的光。中村被授予2006年千年科技奖的发明人。

该技术的发展已引起他们的LED光输出效率，增加指数，与20世纪60年代以来发生的36个月翻一番大约每到，在某种程度上类似摩尔定律。一般的进步归因于其他半导体技术和光学和材料科学的进步并行发展。这种趋势是通常称为Haitz定律后，罗兰博士Haitz。

2008年2月，比尔肯大学大学在土耳其报300瓦每流明光可见光发光效率瓦（而不是每电气），并利用温光纳米晶体。

2009年1月，来自英国剑桥大学的研究人员报告说，为不断发展的氮化矽（氮化镓）LED的镓过程。生产成本可以减少90％，而不是采用2英寸蓝宝石晶圆6英寸硅片。该团队由科林汉弗莱斯。

技术

物理

像一个正常的二极管，发光二极管组成的一个芯片的半导体材料掺杂的杂质，以创造一个pn结。正如在其他二极管，电流流或容易从P端，阳极，到N端，或阴极，但不是在相反方向。电荷载体，电子和洞，从交界处流入电极具有不同的电压。当电子遇到一个洞，它属于一个较低的能级，并释放能量的一个形式的光子。

该波长的发射光，因此它的颜色，取决于带隙能量的 PN 结的材料组成。在硅或锗二极管中，电子和光学发射孔重组由非辐射跃迁而产生没有，因为这些都是间接带隙材料。所用的材料为LED有直接带隙的能量相当于近红外，可见光或近紫外线。

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LED的发展开始用红色和红外设备作出的镓砷化物。在进展材料科学与以往任何时候都取得了波长更短的生产设备的可能，产生光的颜色不同。

发光二极管通常是建立在一个n型衬底附加于p型层的电极，在其表面沉积。P型衬底，而不太常见，也发生。许多商业的LED，尤其是氮化镓/氮化铟镓，还使用蓝宝石衬底。

大多数材料的生产用于LED具有很高的折射率。这意味着，大量光将反映到在关键材料的背面/空气表面界面。因此LED的光提取是一个重要方面LED生产，但以大量的研究和发展。

效率与操作参数

典型的LED指示灯被设计运行不超过30-60 毫瓦的电能[毫瓦]。在1999年左右，飞利浦Lumileds公司推出能够在一个连续的使用功率LED 瓦 [我们]。这些LED采用更大的半导体芯片来处理大型电源输入。此外，半导体芯片都是固定在金属片上，以供热量从LED芯片搬迁。

对LED照明的关键优势之一是它的高效率，其每单位的光输出功率输入测量。.白光LED的匹配，迅速超越了标准的白炽灯照明系统的效率。2002年，Lumileds公司作出瓦的LED可提供5 发光效率的18至22 流明每瓦[流明/瓦]。相比之下，传统的60〜100 W 白炽灯泡生产约15流明/瓦，与标准荧光灯产生高达100流明/ W的一个经常发生的问题是，效率将下降为目前的大幅增加。这种效应被称为下垂，有效地限制了特定的LED光输出的一，增加加热超过光输出更大的电流。

2003年9月，一个蓝色的LED新类型，表明了公司Cree公司，公司提供24毫瓦在20 毫安 [毫安]。这产生了商业包装的白光在20毫安给65流明/瓦，成为最亮的白光LED在商业上可利用的时间，超过4倍效率，标准白炽灯。2006年，他们表现出了创纪录的白光LED 131流明/瓦的发光效率在20毫安的原型。此外，首尔半导体已计划为135流明/ 2007流明和80 × 145 / W的2008年，这将更好地接近以上标准白炽灯和数量级的改善，甚至比标准的荧光灯。[30] 日亚化学公司已开发出白光LED 150流明的发光效率/ W于一正向电流为20毫安。

发光二极管

应当指出，高功率（≥1瓦）LED的普通照明应用的实际需要。这些器件的典型工作电流开始在350毫安的电流。

请注意，这些效率只，在低温实验室举行的LED芯片的。在照明应用，工作在更高的温度和驱动电路损耗，效率非常低。美国能源部（DOE）的白炽灯或节能灯测试的商业LED灯设计，以取代表明，平均疗效仍有约46流明/ 2009年钨（测试时的性能介于17流明/ W到79流明/瓦）。

克里2月3日发出的新闻稿，对2010年的实验室原型在室温下发光二极管实现每瓦208流明。在相关色温据报4579光

寿命和故障

主要文章： LED的失效模式列表

固态装置，如LED是非常有限的受磨损，如果操作在低电流和低的温度。在20世纪70年代和80年代生产的LED的许多服务至今。一生中引述的典型是25,000到100,000小时，但热和当前的设置可以延长或缩短这个时间显着。

症状最常见的LED（和激光二极管）的失败是效率逐渐降低光输出和损失。突发故障，虽然罕见，也可能发生。早期的红色LED值得注意的是他们的短寿命。随着高功率LED发展的设备受到交界处的温度较高，比传统设备提高电流密度。这会导致压力的物质，可能导致早期退化的光输出。为了定量分类的方式在一个标准化的一生已建议使用条款L75和L50的时间，这是一个给定的LED将达到75％和50％的光输出分别。L50相当于半生活中的LED。

像其他照明装置，发光二极管性能的温度依赖性。大多数制造商所公布的LED的评级为25 ° C的工作温度用发光二极管信号灯户外，如交通信号或-路面，而且是在那里的气候利用灯具内的温度会非常热，可能导致失败，甚至低信号强度。

发光二极管保持一致，即使在寒冷的气温光输出，与传统的照明方法。因此，LED技术可能是一个很好的替代冰箱照明等领域的超市，而且会持续时间比其他技术。由于发光二极管不产生像白炽灯泡的热量，它们是一个能源效率的技术，如使用冷冻机等应

发光二极管

用。另一方面，因为他们不会带来太多的热量，冰和雪更冷了，可能就建立在LED灯具气候。这是一个问题困扰着机场跑道的灯光，虽然做了一些研究，试图开发散热技术，以热转移到其他地区的灯具。

实际应用

第一个商用的LED被普遍用作替代白炽灯和霓虹灯标志灯，并在7段显示器，第一次在昂贵的设备，如实验室和电子测试设备，后来在这些设备的电视，收音机，电话，计算器，甚至手表（见名单信号应用）。这些明亮的红色发光二极管是不够只在指标的使用，因为光输出是不够的，照亮的区域。.后来，其他的颜色，也成为广泛使用的器具和设备出现了。.随着技术变得更加先进的LED材料，光输出增加，同时保持了效率和可靠性，以一个可接受的水平。.本发明和轻发展的高功率白光LED灯用于照明（见名单照明应用）。大多数的LED进行了输出非常常见5毫米T1的¾和3毫米T1的软件包，但随着权力，它已成为越来越有必要摆脱过多的热量，以保持可靠性，所以更复杂的软件包已被有效改编散热。先进的软件包为国家的设施，高功率LED承担早期LED的相似性很小。

在低能耗，低维护和现代的LED小尺寸，导致显示申请的状况指标和对各种设备和设施。大面积的LED显示屏所用的球场为动态显示和装饰显示器。薄，轻信息显示用于机场和铁路车站，列车的目的地为显示，公共汽车，电车，轮渡。

单一颜色的光，能提供适合的交通灯和信号，出口标志，应急照明车，船舶灯笼和基于LED圣诞灯饰。在寒冷的气候条件下，LED交通灯可能仍然积雪覆盖。[86]红色或黄色LED的使用和在环境中的字母数字显示指标在夜视必须保留：飞机驾驶舱，潜艇和船舶桥梁，天文观测，并在该领域，如夜间动物观赏和军事领域的使用。

由于他们长期生活和快速开关时间，LED已经被用于汽车的高安装刹车灯，卡车和巴士刹车灯和转向信号，对一些时间，但许多汽车现在使用的LED集群为他们的尾灯。LED的使用也有优势，因为LED的造型与能比白炽灯照明形成更薄更抛物线反射镜。

发光二极管

在采取点亮（或许0.5秒比白炽灯泡快）提高了更多的时间给司机安全作出反应的时间明显改善。据报道，在正常的公路上行驶汽车的长度等于增加了汽车后面的反应时间。白光LED头灯也开始露面。在一个双密度电路（即后方标记和刹车），如果LED的脉冲频率是不是一个足够快的，他们可以创建一个幽灵阵列，其中LED的鬼形象将出现如果眼睛快速扫描整个阵列。

由于产量低的LED相对便宜，他们也用在应用，如许多临时glowsticks，throwies和光子纺织 Lumalive。艺术家们也可用于发光二极管的LED艺术。

天气/全危害无线电接收器与特定地区邮件编码（同）有3个LED：红色的警告，手表橙，并发出黄色的警告时与发言。

照明

主要文章： LED灯

随着高效率，高功率LED的发展已成为可能纳入照明和照明的LED。更换灯泡已以及专用的固定装置和LED灯。LED是作为街灯和其他建筑照明在使用变色。在机械强度，寿命长，是用于汽车照明在汽车，摩托车和自行车灯。

LED已经被用于照明的街道和停车场。2007年，意大利村Torraca首先是转换整个照明系统，发光二极管。

LED的使用日益普遍的水族馆照明。特殊的珊瑚礁水族馆，LED灯提供与减少热量输出效率的光源，以帮助保持最佳温度水族馆。基于LED的水族馆灯具也有被手动调节，以产生特定颜色的珊瑚，鱼类理想的色彩频谱的优势，和无脊椎动物，同时优化photosynethically有效辐射（PAR）的增加，如珊瑚生长和光合生活的可持续性，海葵，蛤和海藻。这些装置可以电子编程，以模拟在一天不同的照明条件，反映了太阳和月亮的分阶段动态礁的经验。LED灯具的成本通常高达5倍，而同样额定荧光灯或高强度放电照明礁水族馆的设计，没有高输出的日期。

LED是现在也被用来在机场和直升机场照明。机场的LED灯具目前包括中等强度的跑道灯，跑道中心线灯照明和阻挠。

也适用于发光二极管背光的液晶电视和轻巧笔记本电脑显示器和光来源的DLP投影机（见LED电视）。RGB LED的增加颜色的发光二极管

色域高达45％。显示器屏幕电视和电脑，可使用越来越薄的LED背光的。

缺乏的红外/热辐射使理想用于LED 舞台灯使用的RGB LED的银行，可以轻松地改变传统的舞台灯光色彩，减少采暖，照明以及医疗在红外辐射是有害的。

由于LED小，坚固耐用，几乎无需电源，他们都是手工使用等装置举行手电筒。的LED 闪灯，或照相机闪光灯工作在一个安全，低电压，相对于250 +伏特发现常见的氙气闪光灯的照明。这一点尤其适用相机到移动电话，其中空间电路是十分宝贵和笨重的电压增加，是不可取的。发光二极管用于照明的红外夜视应用，包括安全摄像机。LED的周围环摄像机，一个旨在向，反光 的背景，使色度键控在影片制作。

LED是用于装饰照明以及。用途包括但不限于室内/室外装饰，豪华轿车，货物拖车，转换车，游船，休闲车，船，汽车，卡车和公用事业。LED照明装饰也可以进来的灯光公司标志，并加强与在电影院和礼堂过道照明形式。

智能照明

光可以被用来传输宽带数据，这已在实施的IrDA标准，使用红外线发光二极管。由于LED可以循环和关闭每百万第二次，他们可以在效应，成为无线路由器的数据传输。[89] 激光也可调制这种方式。

可持续照明

高效照明需要可持续建筑。一个13 30w的LED灯泡生产450到650 流明 [90]。这相当于一个标准的40瓦白炽灯泡[91]。一个标准的40瓦白炽灯泡有一个预期寿命1000小时，而LED的可以继续经营效率与减少超过50,000小时，50倍的白炽灯泡长。

环保选择

单千瓦小时的电力将产生1.34磅（610 g）款二氧化碳排放量。[92]假设平均灯泡是一天10小时，一个40瓦的白炽灯泡会产生196磅（89公斤）每年的二氧化碳。13瓦的LED相当于将只负责跨度为6300磅（29千克）的 CO 2比同一时间。建筑物的碳足迹，从照明，可降低68％，通过交换在气候温暖的新型LED所有白炽灯泡。在寒冷的气候，能源节约可能较低，因为将需要更多的发光二极管

供暖，以弥补较低的温度。

发光二极管也非又名毒性不像更受欢迎节能灯泡选项：紧凑型荧光灯紧凑型荧光灯含有有害的痕迹汞。虽然在一个紧凑型荧光灯小，引入环境少即是最好的汞量。

经济可持续发展

LED灯泡的照明可能是因为他们的寿命很长的家庭或办公空间成本效益的选择。消费者使用的LED作为一种替代传统的照明系统是目前妨碍了高成本和低效率的可用产品。测试结果表明：2009年美国能源部35流明的平均疗效/瓦，低于典型的节能灯，和低至9流明/瓦，比标准的白炽灯泡坏。[90] LED灯泡的初始成本高的商业是由于昂贵的蓝宝石 基板是生产过程的关键。蓝宝石器具必须再加上镜子一样反射光线收集器，否则将被浪费。

2008年，材料科学的研究小组在美国普渡大学成功地在蓝宝石元件LED灯泡生产用的替代品。[93]。该小组使用的金属涂层的硅晶片的一个内置的反射层，氮化锆，以减少LED的整体生产成本。他们预测，在未来数年内，LED的革命，新技术生产的节能灯将具有竞争力的价格。较便宜的LED将不仅是最好的节能器，但也是一个非常经济的灯泡。

非视觉应用

光有许多其他用途除了用于看。LED是用于这些应用程序。在三组的用途秋季：通讯，传感器和光物质的相互作用。

这些LED灯由可调制很快使他们在广泛用于光纤和自由空间光通信。这包括远程控制。，如电视机和录像机，其中红外发光二极管通常使用光电绝缘器使用一个LED一结合光电二极管或光电晶体管两个电路之间提供电气隔离的一个信号通道的。这是特别有用的电压低的地方在医疗设备的信号从一个传感器电路（通常是电池供电的接触）与一个活的有机体，必须是电动操作隔离任何可能的电气故障监控装置在录音或有潜在危险的电压。一个光隔离器还允许资料传输电路之间不共享一个共同的地电位。

许多传感器系统依赖于光作为信号源。LED通常理想作为光源，由于该传感器的要求。LED被用来作为移动传感器，例如在光学计算机鼠标。任天堂的Wii的传感器使用红外线LED酒吧。

发光二极管

在脉搏血氧计测量氧饱和度。一些典型的平板扫描仪的使用，而不是数组的RGB LED的冷阴极荧光灯作为光源。发光颜色有三个独立的控制允许扫描仪校准更精确的色彩平衡本身，也没有必要热身。此外，它的传感器只需要是单色的，因为在页扫描被任何一时间点只能根据的是由一个单一颜色点燃。触摸感应 ：由于LED也可作为用于光电二极管，它们既可以用于发射照片和检测。这可用于，例如触摸感应屏幕，从光线反射或注册一个手指触摸笔。

许多材料和生物系统是敏感的，或依赖于光。拓展灯用发光二极管，以增加光合作用的植物，细菌和病毒可以使用去除水中的其他物质和紫外线 LED的消毒。其他用途的紫外线固化油墨的一些设备和涂料的应用，以及打印机的LED。

LED的使用，特别是有趣的植物修炼，这主要是因为它更节省能源，减少热量产生（可损害植物接近热灯），并能提供最佳的植物生长和开花期比目前使用的光的频率增加至灯： 海港巡逻组（高压钠），氢（金属卤化物）或节能灯 /低能量。但它不取代这些增长灯由于它具有较高的零售价格，为大规模生产和LED产品的开发工具包将变得更加便宜。

发光二极管也被用来作为一种媒介，质量电压参考的电子线路。正向电压降（例如，约1.7 V的一个正常的LED红色）可以用来代替齐纳二极管在低电压稳压器。红色发光二极管具有平坦的我/视频膝盖以上的曲线;氮化物基发光二极管具有相当陡峭的I / V曲线，不应用有助于这一点。虽然LED正向电压电流更比一个好齐纳依赖，齐纳二极管的电压并不普遍低于现有约3五

光来源

机器视觉系统通常需要明亮，均匀的照明，使感兴趣的特征更容易处理。LED通常用于这一目的，这是应用领域的可能仍然地区之一，主要应用到足够低的价格下降，使信号及照明应用更广泛。条码扫描仪是机器视觉最常见的例子，很多便宜的，而不是用红色发光二极管激光器。发光二极管构成的理想光源近的机器视觉系统有几个原因：

在照明领域的规模通常比较小，机器视觉系统往往相当昂贵，因此，光源的成本通常是轻微的关注。但是，它可能不容易更换光源在复杂破碎机械的人选，而在这里，LED的使用寿命长，是一

发光二极管

个好处。

发光二极管的元素往往是小，可与平地，甚至形基板（多氯联苯等），使明亮，均匀的来源可以设计出直射光检查，严格控制对高密度零件放置方向。通常可以得到小，价格低廉镜头和扩散，帮助实现超过照明均匀性的控制水平和高光密度。LED光源可以在多种配置型（用于反射照明射灯;环同轴照明灯，轮廓灯照明回来;线性组合，平面，大尺寸面板，为弥漫性，全方位的照明圆顶来源）。

LED可以很容易地选通（在微秒范围及以下），并与影像同步。高功率LED，可让即使很短的光脉冲明亮的图像。这是经常使用，以获得清晰和锐利“仍然是”快速移动的部分图像。

发光二极管有几种不同的颜色和波长，容易允许使用每个应用程序，不同的颜色可能会提供更好的利益特征能见度最好的颜色。拥有一个精确已知的频谱可以紧密配合，以用于分隔带宽或信息，以减少环境光干扰的影响过滤器。发光二极管通常工作在较低温度下工作，简化管理和热耗散，因此允许塑料镜片，过滤器和扩散器使用。防水单位也可以轻易地被设计为在恶劣或潮湿的环境（允许使用的食品，饮料，石油工业）。

第二篇：实验三 低频功率放大器

实验三

低频功率放大器——OTL功率放大器

（即原资料的实验十六）

一、实验目的

1、进一步理解OTL功率放大器的工作原理。

2、加深理解OTL电路静态工作点的调整方法。

3、学会OTL电路调试及主要性能指标的测试方法。

二、实验仪器

1、双踪示波器

2、万用表

3、毫伏表

4、直流毫安表

5、信号发生器

三、实验原理

图16-1 OTL功率放大器实验电路

图16-1所示为OTL低频功率放大器。其中由晶体三极管T1组成推动级（也称前置放大级），T2、T3是一对参数对称的NPN和PNP型晶体三极管，它们组成互补推挽OTL功放电路。由于每一个管子都接成射极输出器形式，因此具有输出电阻低，负载能力强等优点，T1管工作于甲类状态，适合于作功率输出级。它的集电极电流IC1由电位器RW1进行调节。IC1的一部分流经电位器RW2及二极管D，给T2、T3提供偏压。调节RW2，可以使T2、T3得到合适的静态电流而工作于甲、乙类状态，以克服交越失真。静态时要求输出端中点A的电位UA1UCC，可以通过调节RW1来实现，又由于RW1的一端接在A点，因此在2电路中引入交、直流电压并联负反馈，一方面能够稳定放大器的静态工作点，同时也改善了非线性失真。

当输入正弦交流信号Ui时，经T1放大、倒相后同时作用于T2、T3的基极，Ui的负半周使T2管导通（T3管截止），有电流通过负载RL（用嗽叭作为负载RL，嗽叭接线如下：

只要把输出Uo用连接线连接到插孔LMTP即可），同时向电容C0充电，在Ui的正半周，T3导通（T2截止），则已充好电的电容器C0起着电源的作用，通过负载RL放电，这样在RL上就得到完整的正弦波。

C2和R构成自举电路，用于提高输出电压正半周的幅度，以得到大的动态范围。由于信号源输出阻抗不同，输入信号源受OTL功率放大电路的输入阻抗影响而可能失真，R0作为失真时的输入匹配电阻。调节电位器RW2时影响到静态工作点A点的电位，故调节静态工作点采用动态调节方法。为了得到尽可能大的输出功率，晶体管一般工作在接近临界参数的状态，如ICM，U（BR）CEO和PCM，这样工作时晶体管极易发热，有条件的话晶体管有时还要采用散热措施，由于三极管参数易受温度影响，在温度变化的情况下三极管的静态工作点也跟随着变化，这样定量分析电路时所测数据存在一定的误差，我们用动态调节方法来调节静态工作点，受三极管对温度的敏感性影响所测电路电流是个变化量，我们尽量在变化缓慢时读数作为定量分析的数据来减小误差。※OTL电路的主要性能指标：

1、最大不失真输出功率Pom

21UCC理想情况下Pom，在实验中可通过测量RL两端的电压有效值，来求得实际的

8RL2U0

Pom

（16-1）

RL2、效率η

Pom100%

（16-2）PEPE—直流电源供给的平均功率

理想情况下ηmax＝78.5%。在实验中，可测量电源供给的平均电流Idc（多测几次I取其平均值），从而求得

PEUCCIdc（16-3）

负载上的交流功率已用上述方法求出，因而也就可以计算实际效率了。

四、实验内容

1、关闭系统电源。按图16-1正确连接实验电路。

2、用动态调试法调节静态工作点，先使RW2＝0，Us接地。

3、打开系统电源，用万用表测量Ａ点（即LTP2）电位，调节电位器RW1，使UA

4、关闭系统电源。断开US接地线，连接信号源输出和US。

5、打开系统电源。调节信号源输出f=1KHz、峰峰值为50mV的正弦信号作为Us，逐渐加大输入信号的幅值，用示波器观察输出波形，此时，输出波形有可能出现交越失真（注意：没有饱和和截止失真）

6、缓慢增大RW2，由于RW2调节影响A点电位，故需调节RW1，使UA1UCC。21UCC（在2Us=0的情况下测量）。从减小交越失真角度而言，应适当加大输出极静态电流IC2及IC3，但该电流过大，会使效率降低，所以通过调节RW2一般以50mA左右为宜（即测量LTP4和LTP2，或LTP6和LTP2之间的电压为110mV左右为宜)。注意：

①在调整RW2时，一是要注意旋转方向，不要调得过大，更不能开路，以免损坏输出管。

②输出管静态电流调好，如无特殊情况，不得随意旋动RW2的位置。

测量最大输出功率Pom

1、按上述的实验步骤调节好功率放大电路的静态工作点。

2、关闭系统电源。连接信号源输出和US。输出端接上嗽叭即RL。

3、打开系统电源。调节信号源输出f=1KHz、30mV的正弦信号Ｕs，用示波器观察输出电压ＵO波形。逐渐增大Ui，使输出电压达到最大不失真输出，通过观察示波器得到Uom的峰峰值，再用公式UomUom峰峰值求出Uom的有效值，用万用表的欧姆档测出RL的22阻值，最后下面公式计算出Pom。

2Uom

Pom

RL注意：万用表的欧姆档测出RL的阻值的时候，关闭系统电源，断开电路连线。

五、实验数据

六、问题与结论

1、为何OTL电路会出现交越失真？

第三篇：低频功率放大器课程设计报告

《电路与模拟电子技术》

课程设计报告

低频功率放大器

一、摘要

低频功率放大器的主要应用是对音频信号进行功率放大，本文介绍了具有弱信号放大能力的低频功率放大器的基本原理、内容、技术路线。整个电路主要分为稳压电源、前置放大器、功率放大器、波形变换电路共4 部分。稳压电源主要是为前置放大器、功率放大器提供稳定的直流电源。前置放大器主要是实现电压的放大。功率放大器实现电流、电压的放大。波形变换电路是将正弦信号变换成规定要求的方波信号。设计的电路结构简洁、实用，充分利用到了集成功放的优良性能。实验结果表明该功率放大器在带宽、失真度、效率等方面具有较好的指标、较高的实用性,为功率放大器的设计提供了广阔的思路。

二、关键字

前置放大级电路

功率放大

稳压电源电路

波转换电路

三、总体设计方案论证及选择

根据课设要求, 我们所设计的低频功率放大器应由以下几个部分组成：稳压电路、前置放大、功率放大以及波形变换电路。下面对每个单元电路分别进行论证：

前置放大级：

设计要求前置放大输入交流接到地时，RL=8的电阻负载上的交流噪声功率低于10mw因此要选用低噪音运放。本装置选用的优质低噪音运放NE5532AI。设计要求输入电压幅度为5~700mV时，输出都能以Po≥10W满功率不失真输出，信号需放大几千倍，有考虑到运放的放大倍数与通频带的关系，故采用两级放大，增益调节可用电位器手动调节，也可用自动增益控制，但考虑到题目中的“使用”俩字（例如输入信号不是正弦信号，而是大动态音乐信号），本装置采用手动增益调节。

功率放大级：

根据设计题目要求，在供原则的功率放大可由分立元件组成，也可由集成电路完成。由分立元件组成的功放，如果电路选择好，参数恰当，元件性能优越，且制作和调试的号，则性能很可能高过较好的集成功效。许多优质功放是分立功放。但其中有一个元件出现问题或是搭配不当，则性能很可能低于一般集成功放，为了不至于因过载，过流，过热等损坏还得加复杂的保护电路。

现在市场上也有很多性能优越的集成功放芯片，如TDA2040A,LM1875，TDA1514等。集成功放具有工作可靠，外围电路简单，保护功能较完善，易制作易调试等特点，虽不及顶级功放的性能，但满足并超过本设计的要求问题的。

综上所述，考虑时间紧，在满足要求的前提下，选择易调试的集成功放。

我们熟悉的集成功放有TDA2040A，LM1875，TDA1514等，其中TDA2040A功率量不大，TDA1514外围电路较复杂，且易自激。这两种功放的低频率特征都欠佳，LM1875外围电路简单，电路熟悉，低频特性好，保护功能齐全。它的不足之处是高频特性较差（BW<=70KHz），但对于本设计要求的50Hz~10KHz已足够，因此选用LM1875作功放。

波形变换电路：

直接采用施密特触发器进行变换与整形。而施密特电路可用高精度、高速运算电路搭接而成，也可采用专用施密特触发器构成，还可以选用NE5532P电路构成。

通过比较，本课程设计中施密特电路采用高精度、高速运算放大器LF357构成。

自制稳压电源：

本系统设计采用三端集成稳压电源电路，选用LM7815、LM7915三端集成稳压器。

四、设计方案的原理框图

图1 总体设计

放大通道正弦信号外供正弦信号源弱信号前置放大级变换电路正、负极性对称方波 自制直流稳压电源功率放大级RL=8Ω~220V50Hz

五、总体电路图、接线图及说明 XFG101C210uF2V318 V 683XDA1THDU2A1C458U3B710uF9R5850%050kΩKey=AXSC1Ext Trig+_A+_B+_10NE5532AI746R21MΩ0R415kΩR31kΩ4C347uF0R61MΩ14110R71kΩ12C547uF004NE5532AIR822kΩR9V4-18 V 1350%050kΩKey=A150

图2 前置放大电路

说明：前置放大由两级NE5532典型应用电路组成，各级均采用固定增益输出衰减组成。要求当各级输出不衰减，输入Vp=5mV时，输出Va.pp>=2.53V。

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

图3 功率放大电路

说明：功率放大器选择用集成功放LM1875，采用典型电路，此电路中R3，R2组成反馈网络，C1为直流反馈电容，R1为输入接地电阻，防止输入电路时引入感应噪声，C7为信号耦合电容，D1，D2为保护二极管，R4和C6组成退偶电路，防止功放产生高频自激，C5，C2，C3，C4是电源退耦电容。

六、主要元器件选择

1）稳压电路中选用LM7815、LM7915三端集成稳压器

2）因为LF357属于FET管，具有良好的匹配性能，输入阻抗高、低噪声、漂移小、频带宽、响应快等特点，所以在正弦波一方波转换电路中采用集成运放LF357

3）在前置放大级电路中采用集成双运放NE5532,在功率放大级中采用运放LM1875。

七、电路参数计算

前置放大计算

对于第一级放大，要求在信号最强时，输出不失真，即Vp=700mV时，输出Vom<11V(低于电源电压1V)。所以

A1=Vom/Vp=11/0.7 =15.7 取A1=15.当输入信号最小，即Vpp=10mV，而输出不衰减时

V01.pp=A1*Vi.pp=15*10=150mA 第二级放大要求输出V02.pp>2.53V,考虑到元件误差的影响，取V02.pp=3V，而输入信号最小为150mV，则第二级放大倍数是

A2 = V02.pp/ V01.pp=20 功率放大计算：

LM1875开环增益为26dB，即放大倍数 A=20

因为要求输出到8Ω电阻负载上的功率P0>10 W。而 Vom=2Rl*P。=12.65V 加上功率管管压降2V，则

V=Vom=12.65+2=14.65V 取电源电压为15V

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

八、Multisim仿真结果

前置放大

直流稳压

功率放大

波形转换

九、收获与体会

通过此次课程设计锻炼，我不仅深深体会到理论知识与实践结合的不易，还深入了解并学会了一种简单实用、成本低的低频功率放大器的电路设计方法。课设过程中为了让自己的设计更加完善，更加符合工艺标准，一次次翻阅热处理方面的书籍是十分必要的，同时也是必不可少的。通过这次课程设计我也发现了自身存在的不足之处，虽然感觉理论上已经掌握，但在运用到实践的过程中仍有意想不到的困惑，经过一番努力才得以解决。我懂得了学习的重要性，了解到理论知识与实践相结合的重要意义。

十、参考文献

[1] 胡翔骏 电路分析(第二版)北京：高等教育出版社 2007 [2] 华成英、童诗白 模拟电子学基础（第四版）北京：高等教育出版社 2006 [3] 黄智伟 全国大学生电子设计竞赛系统设计 北京：北京航空航天大学出版社 2006 [4] 夏路易、石宗义 电路原理图与电路板设计教程 北京希望电子出版社 2002 [5] 谷丽华、辛晓宁、么旭东 实用低频功率放大器的设计 沈阳化工学院学报 [6] 高玉良 电路与模拟电子技术 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 图2

直流稳压电路

说明：直流稳压电源部分为整个功放电路提供能量，根据设计的前置放大级电路和功率放大级电路的要求，仅需要稳压电源输出的一种直流电压即+15V。因三端稳压器具有结构简单、外围元器件少、性能优良、调试方便等显著优点，故本设计中采用三端稳压电路。两组独立的20V交流，经过桥堆整流，大电容滤波，再加0.1uF小电容滤掉电源中的高频分量。考虑到制作过程中电源空载时的电容放电可在输出电容并上1K大功率电阻。另外还要给7815，7915来获得+15V、万一输入端短路，大电容放电会使稳压块由于反电流冲击而损坏，加两个二极管可使反相电流流向输入端起保护作用。

V260V140XSC11R410kΩ2D21N4728A5R510kΩR6831Ext Trig+3C1818 V U1A330nF1824NE5532PV370C2-18 V 330nFU2A+_AB_+_R310kΩ700mVrms 1000 Hz 0° 30924NE5532P1kΩD1Key=A1N4728A050% 图5 波形变换电路（NE5532P）

说明：将1KHZ的正弦波变为同频率的对称方波。因LF357属于FET管，具有良好的匹配性能，输入阻抗高、低噪声、漂移小、频带宽、响应快等特点，所以本课程设计中施密特电路采用高精度、高速运算放大器LF357构成，而NE5532运放做隔离用。

第四篇：低频功率放大器概述

第4章 低频功率放大器

【课题】

4.1低频功率放大器概述

【教学目的】

1．了解低频功率放大器基本要求。2．掌握功率放大器的三种工作状态。3．了解功率放大器的常用耦合方式。【教学重点】

1．低频功率放大器基本要求。2．低频功率放大器的分类。【教学难点】

1．低频功率放大器基本要求。2．功率放大器的三种工作状态。【教学参考学时】

1学时 【教学方法】

讲授法 【教学过程】

一、引入新课

1．复习电压放大器主要任务。

2．列举低频功率放大器的应用：如扩音系统或收音机电路中的功放电路。

二、讲授新课

4.1.1低频功率放大电路的基本要求

功率放大器作为放大电路的输出级, 具有以下几个特点和基本要求： 1．能向负载输出足够大的不失真功率

由于功率放大器的主要任务是向负载提供不失真的信号功率，因此，功率放大器应有较高的功率增益，即应有较高的输出电压和较大的输出电流。

2．有尽可能高的能量转换效率

功率放大器实质上是一个能量转换器，它将电源供给的直流能量转换成交流信号的能量输送给负载，因此，要求其转换效率高。

3．尽可能小的非线性失真

由于输出信号幅度要求较大，功放管（三极管）大都工作在饱和区与截止区的边沿，因此，要求功放管的极限参数ICm、PCm、V（BR）CEO等除应满足电路正常工作外还要留有一定余量，以减小非线性失真。4．功放管散热性能要好

直流电源供给的功率除了一部分变成有用的信号功率以外，还有一部分通过功放管以热的形式散发出去（管耗），因此，降低结温是功率放大器要解决的一个重要问题。4.1.2低频功率放大器的分类

1．按电路工作状态分类（1）甲类功放电路

甲类功放电路中的功放管始终工作在三极管输出特性曲线的线性部分如图4.1（a）所示，即在输入信号的整个周期内，功放管始终导通，故电路输出波形失真小，但因静态时，功放管处于导通状态，且静态电流（ICQ）较大，电路转换效率较低，理想情况下最大效率达50%。

（2）乙类功放电路

乙类功放电路在静态时，功放管处于截止状态，如图4.1（b）所示，即在输入信号的整个周期内，功放管只在输入信号的半个周期内导通的。因此，电路需用两只参数基本一致的功放管轮流工作（推挽）才能输出完整的波形信号。由于静态电流为零，电路转换效率较高，理想情况下可达78.5%，但因电路输出波形存在交越失真（注：该内容将在4.2 常用低频功率放大器中学习），需解决失真问题。

（3）甲乙类功放电路

甲乙类功放电路在静态时，功放管处于微导通状态，如图

4.1（c）所示，即在输入信号的整个周期内，功放管只在输入信号的大半个周期内导通。与乙类功率放大器电路一样，需用两只参数基本一致的功放管轮流工作（推挽）才能输出完整的波形信号。由于静态时管子仍然处于导通状态，因此，在输入信号很小时，两个功放管同时都工作，克服了交越失真。电路转换效率略低于乙类，原因是静态时电路中仍有很小的电流，电路会消耗部分电源功率。

图4.1 功放管的三种工作状态 2．按耦合方式分类

（1）阻容耦合功放电路——功放电路输出端通过耦合电容连接负载，如：OTL功放电路。（2）变压器耦合功放电路——功放电路输出端通过变压器连接负载。变压器具有阻抗变换作用，可使负载获得最大功率，但由于有变压器体积大、损耗大、频率特性差等不足之处，目前应用不多。

（3）直接耦合功放电路——功放电路输出端无需通过任何元件而直接与负载相连，如：OCL功放电 路及集成功放电路。

三、课堂小结

1．低频功放电路的基本要求。2．低频功放电路的分类。

四、课堂思考

P97思考与练习题1、2、3。

五、课后练习

P108

一、填空题：1~4；

二、判断题：2；

三、选择题：1~4。

第五篇：专业英语低频功率放大器翻译

低频功率放大器（G题）

湖北师范学院 吴 龙 霍姣姣 许成龙

赛前辅导教师：彭 琦 周兆丰 田开坤 曹庭水 文稿辅导教师:侯向锋 张学文

摘要：本设计主要由低噪声放大电路、带阻滤波电路、信号放大电路、功率放大电路、峰值检波电路、单片机控制、AD转换、LCD显示、稳压电源等电路组成。低噪声放大电路选取甚低噪声宽带高精度运算放大器OP37，并采用并联负反馈结构，具有良好的抗共模干扰能力。带阻滤波器在50Hz频率点输出功率衰减≥6dB，阻带频率范围为43～57Hz，有效滤除了工频噪声的干扰。功率放大电路采用的是双MOS晶体管的甲乙类推挽放大电路。设计的低频功率放大器的通频带为6Hz～150kHz，很好地完成了通频带的扩展。该设计采用的电路结构简单，选取的器件价格便宜。测试结果表明，该低频功率放大器可以很好地实现对低频信号的放大作用，具有较高的实用性，其输出带宽、功率、效率等都达到了较高的指标，为低频功率放大器的设计提供了广阔的思路。关键词：功率放大器、OP37、MOS晶体管、输出功率

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