Shulou(Shulou.com)11/24 Report--

In 1883, the famous inventor Thomas Edison (Thomas Edison) observed a strange phenomenon in an experiment.

At that time, he was testing the life of the filament (carbon filament). Next to the filament, he placed a copper wire, but the copper wire was not connected to any electrode. In other words, the copper wire is not electrified.

After the carbon wire is energized normally, it begins to glow and heat. After a while, Edison turned off the power. He inadvertently discovered that an electric current was also generated on the copper wire.

Edison could not explain the reason for this phenomenon, but as a shrewd "businessman", the first thing he thought of was to patent the discovery. He also named this phenomenon the "Edison effect".

Edison now we know that the essence of the Edison effect is hot electron emission. In other words, after the filament is heated, the electrons on the surface become active and "escape", resulting in being captured by the copper wire, resulting in an electric current.

After applying for a patent, Edison did not think of the use of this effect, so he put it on the shelf.

In 1884, British physicist John Ambrose Fleming (John Ambrose Fleming), a technical adviser to Edison Electro Optics, visited the United States to meet with Edison. Edison showed Fleming the Edison effect he had discovered and left a deep impression on Fleming.

Fleming, this Fleming, everyone should be familiar with it. He is an electrical expert and an electrical engineer. He invented the right-hand rule that is often used in our middle school.

In addition to traditional electricity, Fleming actually has one strong point, which is radio magnetism. When he was young, he studied under Maxwell, specializing in wireless electromagnetic theory. In Maxwell's deathbed class, only two students came to listen, one of which was Fleming.

After watching the demonstration of the Edison effect, Fleming had no idea what the effect could be used for. In fact, it was more than a decade later when he actually used it.

In 1896, the Italian Galilmo Marconi (Guglielmo Marconi) successfully obtained the world's first wireless telegraphy system patent, which brought mankind into the era of wireless communication.

In 1899, Marconi decided to try long-distance radio communications across the Atlantic. In order to accomplish this feat, he called Fleming and signed him up to help improve his radio transmitter and receiver.

Fleming did live up to Marconi's expectations, greatly improved Marconi's design and helped realize the transatlantic wireless communication experiment. (unfortunately, Marconi deliberately concealed Fleming's contribution and "forgot" his promise to award Fleming 500 shares, which angered Fleming half to death. )

Fleming encountered many technical challenges in improving the wireless communication system. Among them, the biggest challenge is the reception of wireless signals.

To put it simply, at the receiving end, how to detect the signal, amplify the signal, so that the signal can be perfectly interpreted.

Everyone knows how to amplify the signal, so what is the detection signal?

The so-called signal detection is actually signal screening. The signals received by the antenna are very messy and there are all kinds of signals. The signal we really need (the signal with a specified frequency) needs to be "filtered" from these messy signals, which is detection.

Unidirectional conductivity (unidirectional conductivity) is the key to realize detection.

As we all know, radio electromagnetic waves are high-frequency oscillations with frequencies as high as hundreds of thousands of times per second. The induced current generated by wireless electromagnetic waves also changes with the "positive, negative, positive and negative". If we use this current to drive headphones, one positive and one negative is zero, the headphones will not be able to reflect the signal.

With unidirectional conductivity, the negative half cycle of the sine wave is gone, all positive, and the current direction is the same. After filtering out the high frequency, the headset can easily reflect the change of the current.

Remove the negative half-week, the current direction becomes consistent, easy to interpret here, I would like to introduce one thing to you first-the ore geophone.

In 1874, German scientist Karl Braun (Karl Ferdinand Braun) discovered that some natural ores (metal sulfides) have the characteristics of unidirectional current conduction and can be used for rectifying (changing alternating current into direct current).

In 1894, British Indian physicist Jagdish Chandra Bos (Jagadish Chandra Bose), based on the discovery of Karl Braun, made the world's first geophone, the ore geophone, using the unidirectional conductivity of galena (lead sulfide).

In 1900, the American Greenleaf Whitler Picard (Greenleaf Whittier Pickard), based on the ore geophone, successfully made the world's first ore radio. This laid the foundation for the rapid popularization of radio broadcasting.

Fleming used ore geophones when studying how to improve the radio receiver. But he thought of the previous Edison effect, and he thought-- could a new type of geophone be designed based on the electron flow of the Edison effect?

Thus, in 1904, the world's first vacuum electronic diode was born under Fleming's hands. At that time, the diode was also called "Fleming valve". Vacuum tubes, vacuum tube, or electronic tubes, are sometimes called "bile ducts". )

Fleming's diode, Fleming's diode, has a very simple structure: a vacuum glass bulb stuffed with two poles: a cathode (Cathode) that emits electrons when heated, and an anode (Anode) that receives electrons.

The reason why there is a vacuum in the glass tube of the side-heating diode is to prevent gas ionization, affect the normal electron flow and destroy the characteristic curve. Vacuum can also effectively reduce the oxidation loss of the filament. )

The emergence of diodes solves the requirements of detection and rectification. However, there is room for improvement.

In 1899, Marconi was invited to the United States to give a radio show. His performance attracted the attention of a young man. This young man is De Forest Lee, who has just received his doctorate.

De Forrest was fascinated by Marconi's radio. So he sent his resume and wanted to join Marconi's company. As a result, he was rejected.

After being rejected, de Forrest did not give up, but continued to study radio communications. His eyes were on Fleming's diode.

In 1906, de Forrest skillfully added a grid plate ("grid") to the vacuum diode and invented the vacuum Triode.

The main function of the Triode grid invented by de Forrest is to control the current.

A small change in the current on the gate can cause a great change in the current of the anode, and the waveform of the change is completely consistent with the gate current. Therefore, the Triode has the function of signal amplification.

Now it seems that the invention of vacuum transistor is a milestone in the field of electronics industry.

This small element integrates the functions of detection, amplification and oscillation, which lays a foundation for the development of electronic technology.

At first, the transistor was a single gate, then it became a double gate with two plates sandwiched together, and then it simply became a whole enclosed grid.

Vacuum tube vacuum transistor was the heart of the electronic industry in that period. Based on it, we have more and more powerful radio stations, radios, gramophones, movies, radio stations, radar, radio intercom and so on.

The internal structure of the vacuum tube radio (you can see many vacuum tubes) de Forrest invented the Triode and soon got caught up in patent lawsuits with Fleming and Marconi.

The two sides sued each other, and Fleming believed that de Forrest had infringed his diode patent, while de Forrest thought his improvement was big enough to form a new patent. The lawsuit lasted for a long time, and finally, the two sides reached a settlement, authorizing each other to produce diodes (transistors).

After the birth of the transistor, because it can amplify the signal, it has been concerned by the American communications giant AT&T.

At that time, AT&T planned to build a transcontinental telephone line connecting the east and west coasts of the United States, and there was an urgent need to solve the problem of signal amplification. Before there is no Triode, the repeater can only be used to amplify the signal, but the effect of the repeater is not good, and the cost is high.

The emergence of the transistor has brought new options to AT&T.

In July 1913, after some haggling, AT&T bought de Forrest's transistor patent for $390000.

Later, AT&T recognized the important role of basic research such as tubes for the development of the industry, and formally established Bell telephone Laboratories in 1925. This company was later known as Bell Labs.

From 1912 to 1920, Western Electric (WE) developed a practical spherical electronic Triode, which is called "onion" tube by enthusiasts.

In 1924, the American RCA Company (Radio Corporation of America) developed a three-pole vacuum tube with high efficiency. This kind of classical tube was widely used in World War I.

In 1919, Germany's Schottky proposed the idea of adding a curtain grid between the gate and the positive. This idea was realized by England's Lund in 1926. This was later known as the Tetrode. Later, Holst and Tellegen in the Netherlands invented the pentode.

In the 1940s, computer technology research entered the most exciting part. It has been found that the unidirectional conduction characteristics of electron tubes can be used to design some logic circuits (such as and gate circuits, or gate circuits). So they began to introduce electronic tubes into the field of computers.

In 1946, Eckert, an engineer at the University of Pennsylvania, and Maoshili, a physicist, jointly developed the first general-purpose electronic computer in the real sense-ENIAC.

Everyone should know that Eniak. This steel giant, which uses more than 18000 electronic tubes and weighs more than 130T, covers an area of more than 170m2 and can perform more than 5000 addition operations per second. The previous computer needed two hours to complete the computing task, while the ENIAC took only three seconds, which was a miracle at the time.

In the 1940s and 1950s, the development of electronic tubes reached the most exciting part. However, with the progress of technology, people find that electronic tubes have been unable to meet the needs of product design.

On the one hand, the electronic tube is easy to damage, the failure rate is high, on the other hand, the electronic tube needs to be heated, a lot of energy is wasted on heating, but also brings a very high power consumption.

So, people begin to wonder if there is a better way to detect, rectify and amplify the circuit.

Let's take a look at the next issue, "what on earth is a transistor".

References:

1. Leo's microelectronics study notes, Li Youbai Leobai,B station

2. The 100-year history of Chinese radio from Shanghai, Dai Hui

3. From tube to transistor, the history of decoding technology, CCTV

4. How vacuum diodes work, Mr. IC

5. The story behind the first transistor, the Chinese University of Science and Technology Hu did not return.

This article comes from the official account of Wechat: fresh Jujube classroom (ID:xzclasscom), author: Xiaozaojun

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