In order to improve the magnification of the electron tube, another grid called curtain grid is added between the anode and the control grid of the triode to form a quadrupole. Because the positive voltage of the curtain grid is much higher than that of the cathode, it is also a powerful accelerating electrode, which can make electrons reach the anode at a higher speed. In this way, the control function of the control gate becomes more significant, so it has a larger magnification than that of the triode. However, due to the acceleration of electrons by the grid, high-speed electrons hit the anode, and these high-speed electrons have great kinetic energy, so they will hit the so-called secondary electrons from the anode. Some of these secondary electrons will be absorbed by the screen grid to form the screen grid current, which will lead to the reduction of the screen grid voltage, thus reducing the anode current. World Wide Web
In order to solve the above contradiction, a pair of collector electrodes connected to the cathode are added on both sides outside the screen grid of the tetrode. Because the potential of the collector is the same as that of the cathode, they repel electrons, so that the electrons pass through the screen and advance in a certain direction under the action of the collector to form a flat beam. The electron density of this plane electron beam is very high, so a low pressure region is formed. The secondary electrons from the anode are pushed back to the anode due to the repulsion of this low voltage region, which greatly reduces the screen current and enhances the amplification ability of the electron tube. This kind of electron tube is called beam quadrupole tube, which not only has higher magnification than triode, but also has larger anode area and allows more current to pass through, so it is often used as power amplifier in current amplifier.
A Milestone in the Development of Electronic Technology —— Transistor
When it comes to transistors, many people may feel strange. However, it was the invention of small transistors that brought a revolution to electronics. The rapid development and wide spread of this revolution completely exceeded people's imagination.
At present, transistors and microcircuits are almost omnipotent and ubiquitous. From hearing AIDS, radios, tape recorders and televisions in people's daily lives to laboratory instruments, industrial production and national defense equipment, computers, robots and frisbees, they are inseparable. It is no exaggeration to say that transistors have laid the foundation of modern electronic technology.
However, what exactly is a transistor? How was it invented? An indispensable step-the advent of electron tubes 1883, Edison, a world-famous inventor, invented the first incandescent lamp. The invention of electric light has brought light and warmth to people who have been living in darkness. In this process, Edison also discovered a strange phenomenon: a piece of red-hot iron will emit an electron cloud, which is the later Edison effect. 100000010/06 The British inventor Fleming traveled across the ocean to the United States and met Edison, whom he had admired for a long time. In the meeting of two great inventors, Edison once again showed the Edison effect. Unfortunately, due to the limitation of technical conditions at that time, both Edison and Fleming were puzzled by this effect and did not know how to deal with it.
At the beginning of the 20th century, the wired telegraph came out. This invention has brought a lot of convenience to people. The signal sent by cable telegraph is a high-frequency radio wave, and the receiving station must rectify it to hear the sound sent by the receiver. At that time, the rectifier was complex in structure and poor in efficiency, and it was in urgent need of improvement. Fleming's brainwave of high-frequency rectifier is being studied. He thought, what would happen if the Edison effect was applied to the detector? In this way, a new invention came out.
1904, Fleming added a flat electrode in front of the wire (filament) heated in vacuum, thus inventing the first electron tube. He called this electron tube with two electrodes a diode. With the newly invented electron tube, the current can be rectified and the telephone receiver or other recording equipment can work. Now, when we turn on an ordinary tube radio, we can easily see the tube with a red filament. It is the heart of electronic equipment.
Fleming diode is a brand-new invention. It works very well in the laboratory. However, due to some reasons, it is not successful in the practical application of geophone, which is not as reliable as the mineral geophone invented in the period. So it had no influence on the development of radio at that time.
Shortly thereafter, the poor American inventor deforest skillfully added a grid plate between the filament and the diode plate, thus inventing the first vacuum triode. This small change has brought unexpected results. It not only responds more sensitively, but also makes music or sound vibrate, integrating three functions of detection, amplification and oscillation. Therefore, many people regard the invention of triode as the real starting point of electronic industry. Deforest himself was very surprised and thought that "I found an invisible empire in the air". The appearance of electron tubes promoted the vigorous development of radio electronics. By about 1960, the annual output of the radio industry in western countries has reached10 billion electron tubes. Electron tubes are not only used in telephone amplifiers, maritime and air communications, but also widely penetrated into the fields of family entertainment, broadcast news, educational programs, literature and music, and entered thousands of households. Even the invention and further development of airplanes, radars and rockets were aided by electron tubes.
The magician's three-legged electron tube was once a convenient tool in electronics research. Electron tube devices have been dominant in the field of electronic technology for more than 40 years. However, it is undeniable that the electron tube is very large, consumes a lot of energy, has a short life, is noisy and its manufacturing process is very complicated. Therefore, shortly after the advent of the electron tube, people are trying to find new electronic devices. In World War II, the shortcomings of electron tubes were even more exposed. Ordinary electron tubes used in radar operating frequency band are extremely unstable. Electronic tubes used in mobile military instruments and equipment are clumsy and prone to failure. Therefore, the inherent weakness of the electron tube and its urgent wartime demand have prompted many scientific research units and scientists to concentrate their efforts and quickly develop solid components that can replace the electron tube.
As early as 1930s, people have tried to manufacture solid electronic components. But at that time, most people imitated vacuum triode to make solid triode directly, so all these attempts failed without exception.
One day in June 2008, in a room of Bell Laboratories, a very ordinary radio was playing soft music, and many visitors stopped in front of it. Why does everyone have a soft spot for this radio? It turns out that this is the first radio with a new solid component-transistor instead of electron tube. Although people are interested in this radio, they don't think highly of the transistor itself. A reporter from the New York Herald Tribune wrote in the report: "This device is still in the laboratory stage, and engineers all think that its innovation in the electronics industry is limited." In fact, after the invention of the transistor, it won't be long.
What is a transistor? Generally speaking, transistors are solid electronic components made of semiconductors. Metals such as gold, silver, copper and iron. It has good electrical conductivity and is called a conductor. Wood, glass, ceramics, mica, etc. It is not easy to conduct electricity and is called an insulator. A substance with conductivity between a conductor and an insulator is called a semiconductor. Transistors are made of semiconductor materials. The most common materials are germanium and silicon.
Semiconductor is a material discovered at the end of 19. At that time, people didn't find the value of semiconductors, so they didn't pay attention to the research of semiconductors. Until World War II, due to the development of radar technology, the application of semiconductor device-microwave ore detector became more and more mature, and played an important role in the military, which aroused people's interest in semiconductors. Many scientists devote themselves to the in-depth study of semiconductors. After intense research work, American physicists shockley, Badin and bratton beat us to it and jointly invented the transistor, a semiconductor solid element with three fulcrums. Transistors are called "three-legged magicians". Its invention is an epoch-making event in the history of electronic technology, which opens a brand-new era-the era of solid-state electronic technology. The three of them also obtained 10 because they studied semiconductors and discovered the transistor effect.
Shockley Group and Transistor American william shockley, 19 10 was born in London on February 3rd, and studied quantum physics at MIT. 1936 After receiving his doctorate from this school, he entered the prestigious Bell Laboratory, which was founded by Bell, the inventor of telephone. Bell Laboratories is the most famous research institute in the field of electronics, especially in the field of communication. Known as the "research kingdom", as early as 1936, Mervyn Kelly, then director of the research department and later president of Bell Laboratories, told shockley that in order to meet the growing communication demand, the mechanical conversion of the telephone system would be replaced by electronic exchanges in the future. This passage left an indelible impression on shockley and aroused his enthusiasm. He devoted his life to the cause of promoting the progress of electronic technology. Walter brattain is an American, too. He was born in Xiamen on February 1902, a beautiful city in the south of China. At that time, his father was employed to teach in China. Bratton is an experimental expert. Badin 1929 was born in Madison, Wisconsin, USA in 1908 after receiving his doctorate from the University of Minnesota. He received two degrees from the University of Wisconsin: 1928 and 1929. Later, he transferred to Princeton University to study solid state physics. 1936 received a doctorate. 1945 came to work in Bell Laboratories. Mervyn Kelly is a visionary technology manager. Since 1930s, he has been paying attention to finding and adopting new materials and electronic amplification devices working according to new principles. Around the Second World War, his keen scientific insight prompted him to resolutely decide to strengthen the basic research of semiconductors in order to open up new fields of electronic technology. 1in the summer of 945, Bell Laboratories officially decided to take solid-state physics as the main research direction, and made a huge research plan for it. Inventing the transistor is an important part of this plan. 1946 In the summer, the solid-state physics research group of Bell Laboratories was formally established. This group is headed by shockley and several groups under its jurisdiction. One of them is a semiconductor group, including bratton and Badin. There are many talents in this group, such as theoretical physicists, experimental experts, physical chemists, circuit experts, metallurgical experts, engineers and so on. Working together, they are good at learning from the beneficial experience of their predecessors, but also pay attention to learning from the research results of their contemporaries and absorbing the strengths of many people. Useful academic discussions are widely carried out in the group. "If there are new ideas and new questions, they will be called."
At first, when bratton and Badin studied transistors, they adopted the concept of field effect proposed by shockley. The idea of field effect is the first concrete scheme of solid-state amplifier proposed by people. According to this scheme, they tried to imitate the principle of vacuum triode and control the movement of electrons in semiconductor with external electric field. However, contrary to expectations, the experiment failed repeatedly.
The effect people get is far less than expected. It's puzzling. Why does theory always contradict practice?
What's the problem? After many sleepless nights of hard thinking, Badin put forward a new theory-surface state theory. The theory holds that surface phenomena will cause signal amplification effect. The introduction of the concept of surface state has made people's understanding of semiconductor structure and properties take a big step forward. Bratton and others carried out a series of experiments carefully. As a result, they unexpectedly found that when the sample and the reference electrode were placed in the electrolyte, a charge layer and electricity appeared inside the semiconductor surface. This discovery excited everyone. In great excitement, they used field effect to speed up their research and repeat experiments. Unexpectedly, a completely different effect suddenly appeared in the continuing experiment. The new situation that followed greatly exceeded the experimenter's expectation.
People's thinking was interrupted, and the original plan of making practical devices had to be changed, and the increasingly clear situation became confusing again. However, shockley's team did not give up. They closely followed the glimmer of light in the vast fog, changed their thinking and continued to explore. After many analyses, calculations and experiments, people finally got the long-awaited ". Badin and bratton put two contact wires on the surface of germanium semiconductor wafer. Amplification occurs when two contact lines are very close. The world's first solid-state amplifier transistor was also born. At this moment worthy of celebration, bratton held back his inner excitement and meticulously wrote in his experimental notes: "Voltage gain 100, power gain 40. The current loss is 1/2.5 ... The people who witnessed and heard the audio were Gibney, Moore, Bardeen, Pearson, shockley, Fletcher and Bowen. "In bratton's notes, Pearson, Moore and shockley signed the date and name respectively to show their approval.
The transistor successfully tested by Badin and bratton is a point contact between a metal contact line and a semiconductor, so it is called a point contact transistor. This transistor can amplify current and voltage.
Based on the rigorous scientific attitude after the invention of the transistor, Bell Laboratories did not immediately announce the research results of shockley Group. They believe that it takes time to understand the function of transistors in order to write papers and apply for patents. After that, shockley and others were busy with their work in a state of extreme tension. There is a trace of worry in their hearts. If others also invented the transistor and announced it first, their efforts would be in vain. Their worries are not excessive at all. At that time, many scientists were concentrating on this subject. At the beginning of 0948, at a meeting in american physical society, Bray and Benzer of Baidu University reported their experiments and findings about point contact of germanium. At that time, the secret of Bell Laboratories' invention of the transistor had not been made public. Bratton, one of its inventors, is sitting in the audience at the moment. Bratton clearly realized that the experiment of Bray and others was only a small step away from the invention of the transistor. Therefore, when Dambray and bratton talked about their experiments after the meeting, bratton immediately became nervous. He didn't dare to talk much, only let the other party talk, for fear of revealing the secret to the other party, and then hurried away. Later, Bray said regretfully, "If I put the electrode near Benze's electrode, I will regret it." The powerful Bell Laboratories are only slightly better in this competition of wisdom and skills.
Six months after the invention of the transistor, on June 30th, 1948, Bell Laboratories showed the transistor to the public for the first time in new york. This great invention surprised many experts. However, most people doubt its practical value. On July 30th of that year, The New York Times reported the news that should have shocked the world in the form of only eight sentences of 20 1.
Indeed, the point contact transistor at that time, like the ore detector, was unstable, noisy, low in frequency, low in magnification, and its performance could not keep up with that of the electron tube, making it difficult. No wonder people are indifferent to this. However, physicist Shockley and others firmly believe that the transistor has a bright future and its great potential has not been realized. So after the invention of point contact transistor, they spared no effort. Keep studying. After more than a month of repeated thinking, shockley lost weight and his eyes were bloodshot. However, an idea became more and more clear in his mind, that is, the fundamental reason for the failure of previous research was that people blindly imitated vacuum triode regardless of everything. This actually entered the misunderstanding of research. Transistors and electron tubes are produced from completely different physical phenomena, which means that the transistor effect has its own uniqueness. Knowing this, shockley immediately decided to give up the original field effect transistor and concentrate on another idea-transistor amplification. The right idea finally produced the most beautiful flowers. 10, shockley conceived a new transistor, whose structure is like a sandwich bread, with a layer of N-type semiconductor sandwiched between two layers of P-type semiconductor. Good one! Unfortunately, due to the limitation of technical conditions at that time, research and experiment were very difficult. It was not until 1950 that the first PN junction transistor was successfully manufactured.
The emergence of a landmark transistor in the history of electronic technology development is a wonderful flower in the tree of electronic technology. Compared with electron tubes, transistors have many advantages: ① The components of transistors are not consumed. No matter how good the electron tube is, it will gradually deteriorate due to the change of cathode atoms and chronic air leakage. For technical reasons, the same problem existed at the beginning of transistor production. With the progress of material production and various improvements, generally speaking, the life of transistors is 65,438+000 to 65,438+0000 times longer than that of electron tubes, which can be called permanent devices. (2) the transistor consumes very little electrons, only one-tenth or one-tenth of the electron tube. It does not need to heat the filament like an electron tube to generate free electrons. A transistor radio can listen to it for half a year with only a few dry batteries. It is difficult to do this for electron tube radios. The transistor works as soon as it is turned on. For example, a transistor radio will ring as soon as it is turned on, and a transistor TV will display images as soon as it is turned on. Electron tube equipment can't do this. After the machine is turned on, it will take a while to hear the sound and see the picture. Obviously, transistors have great advantages in military, measurement and recording. ④ The transistor is solid and reliable, 65,438+more reliable than the electron tube. This is unmatched by electronic tubes. In addition, the volume of transistor is only 1/10 to 1/100 of that of electron tube, so it can be used to design small, complex and reliable circuits. Although the manufacturing process of transistor is precise, it is simple, which is beneficial to improve the installation density of components. Because of its superior performance, the transistor is widely used in industrial and agricultural production, national defense construction and people's daily life after its birth. 1953, the first batch of battery-powered transistor radios were warmly welcomed as soon as they were put on the market, and people rushed to buy them. Then, a competition was held among manufacturers to make short-wave transistors. Soon after, pocket-sized "transistor radios" without AC power began to be sold all over the world, which triggered a new consumption boom.
Silicon transistor is one of the most popular products in the electronic industry, because it is suitable for working at high temperature and can resist the influence of the atmosphere. Starting from 1967, if electronic measuring instruments or TV cameras are not transistorized, you can't sell any of them. Portable transceivers and even large transmitters in vehicles use transistors.
In addition, transistors are particularly suitable for switches. They are also the basic components of the second generation computer. People often use silicon transistors to make infrared detectors. Even solar cells that can convert solar energy into electric energy can be made of transistors. This kind of battery is an indispensable power supply for satellites traveling in space. Transistor is a small and simple semiconductor element, which is also used in sewing machines. Electric drills and fluorescent lamps have opened the way to electronic control. During the decade from 1950 to 1960, the major industrial countries in the world have invested huge amounts of money in the research and development and production of transistors and semiconductor devices. For example, pure germanium or silicon semiconductor has poor conductivity, but after adding a small amount of other elements (called impurities), the conductivity will be greatly improved. However, if quantitative impurities are to be melted correctly. It must be heated at a certain temperature. Once the temperature is higher than 75 degrees Celsius, the transistor will start to fail. In order to overcome this technical difficulty, the US government has invested millions of dollars in industry to develop this new technology. With such strong financial support, it won't take long. People have mastered the purification, melting and diffusion technology of this high melting point substance. Especially after the power of transistors is increasingly exposed in military planning and space navigation, countries all over the world have launched fierce competition for the dominant position in the electronic field. In order to realize the miniaturization of electronic equipment, people have given huge financial support to the electronic industry at all costs.
Since 1904 Fleming invented vacuum diode and 1906 deforest invented vacuum triode, electronics has developed rapidly as a new subject. But the real rapid progress of electronics should start after the invention of transistors, especially the appearance of PN junction transistors, which opened a new era of electronic devices and caused a revolution in electronic technology. In a short period of more than ten years, the emerging transistor industry has quickly replaced the position of the electron tube industry through years of struggle with invincible ambition and reckless momentum of young people, and has become the vanguard in the field of electronic technology. The foundation of modern electronic technology is real, and the invention of electron tube has revolutionized electronic equipment. However, the tube is fragile and unreliable. Therefore, the advent of the transistor is considered as one of the greatest inventions of this century. It solves most of the problems existing in electron tubes. However, the emergence of a single transistor still cannot meet the needs of the rapid development of electronic technology. With the popularization of electronic technology and the increasingly complex development of electronic products, more and more electronic devices are used in electronic equipment. For example, the B29 bomber that appeared at the end of World War II was equipped with 1 1,000 electron tubes and 1 1,000 radio elements, not to mention electronic computers. The general computer listed in 65,438+0,960 has 65,438+0,000 diodes and 25,000 transistors. A transistor can only replace an electron tube. Millions of transistors can be used in extremely complex electronic devices. A transistor has three legs, and some complex devices may have millions of solder joints. If you are not careful, it is very likely that something will go wrong. In order to ensure the reliability of equipment and reduce its weight and volume, people urgently need to make new breakthroughs in the field of electronic technology. 1957, the Soviet Union successfully launched the first artificial satellite. The news that shocked the world caused a great shock to the American government and the public, which seriously dampened the self-esteem and superiority of Americans. Developed space technology is based on advanced electronic technology. In order to win the leading position in space technology, the US government established the National Aeronautics and Space Administration on 1958, which is responsible for military and space research. In order to realize the miniaturization and lightweight of electronic equipment, astronomical funds have been invested. It is under the stimulation of this fierce arms race that a new technology was born on the basis of the existing transistor technology, that is, integrated circuit, which shines brilliantly today. With integrated circuits, computers, televisions and other devices closely related to human social life are not only small in size, but also small in size. An integrated circuit is a tiny semiconductor chip of several square millimeters, which integrates thousands of transistors, resistors and capacitors, including connecting wires. It's really a place where thousands of troops are deployed. It is an organic combination of materials, components and transistors.
The appearance of integrated circuits is inseparable from transistor technology. Without transistors, there would be no integrated circuit. In essence, integrated circuit is the continuation of the most advanced transistor epitaxial planar crystal manufacturing process. The concept of integrated circuit is closely related to transistor. 1952, dammer, a famous scientist at the royal radar institute, pointed out at a meeting: "with the appearance of transistors and the comprehensive research of semiconductors, it seems conceivable that the future electronic equipment will be solid components without connecting wires." Dahmer's idea has not been put into practice, but it points out the direction for people's in-depth research.
Later, kilby, an American, followed Dammer's footsteps and embarked on the rugged road of studying solid components. Kilby graduated from the Electrical Engineering Department of the University of Illinois. By chance, kilby attended a lecture on transistors in Bell Laboratories. Kilby, who was very creative, was fascinated by transistors at once.
He was in charge of a hearing aid research project in a company at that time. Kilby, who cares about transistors, couldn't help but want to use transistors in hearing AIDS, and it really succeeded. He developed a simple method to mount the transistor directly on the plastic sheet and seal it with ceramics. His initial success made him more and more interested in transistors. Kilby entered Texas Instruments on May 1958 in order to seek greater development. At that time, the company was participating in a micro-component project of the US Communications Force. Kilby is eager to demonstrate his skills in this project. His strong self-esteem prompted him to devote himself to this project with his wisdom and hard work. So he often buries himself in the factory and thinks about the method of making the whole circuit with semiconductors. I can't remember how many times I thought hard, tried and suffered setbacks. After working alone for a long time, it was integrated in 1959.
In March of the same year, the product was exhibited at the Society of Radio Engineers. Shepard, then vice president of Texas Company, proudly announced that this was "the most important development achievement of Texas Instruments after silicon transistors". The rapid development of integrated circuits based on transistor technology has brought rapid progress in microelectronics technology.
The continuous progress of microelectronics technology has greatly reduced the cost of transistors. In 1960, it cost 1 0 to produce 1 transistor, but today, the cost of embedding 1 transistor in integrated circuits is less than1cent, which makes the transistor more widely used.
Moreover, microelectronics technology will fundamentally change human life through miniaturization, automation, computerization and robotics. It affects many aspects of human life: labor and production, family, politics, science, war and peace.