Vacuum Tubes: The World Before Transistors
在任何现代电气设备中，从闹钟、电话、电脑到电视，你都能找到一种叫做晶体管的装置。事实上，你会发现数十亿个晶体管。晶体管是现代计算的原子，它们组合成逻辑门，从而实现计算。1947 年晶体管的发明开启了信息时代的大门。
In any modern-day electrical device—from alarm clocks to phones to computers to televisions—you’ll find a device called a transistor. In fact, you’ll find billions of them. Transistors are the atoms of modern-day computing, combining to create the logic gates that enable computation. The invention of the transistor in 1947 opened the door to the information age as we know it.
But computers existed before transistors did, albeit in a rather rudimentary form. These massive systems took up entire rooms, weighed thousands of pounds, and for all that, were nowhere near as powerful as the computers that we can fit in our pockets today.
但在晶体管出现之前，计算机就已经存在了，尽管当时的形式还相当简陋。这些庞大的系统占据了整个房间，重达数千磅，尽管如此，其功能远没有今天我们口袋里的电脑强大。
这些巨型计算机不是由晶体管构成的，而是由一种叫做热离子阀（又称真空管）的东西构成的。这些看起来像灯泡的设备现在或多或少已经过时了（只有一两个明显的例外），但在它们的鼎盛时期，它们对许多电子系统的设计至关重要，从收音机到电话再到计算机，不一而足。在本文中，我们将了解真空管的工作原理、它们消失的原因以及它们没有完全消失的原因。
Rather than being built out of transistors, these behemoth computers were made up of something called thermionic valves, aka vacuum tubes. These lightbulb-looking devices are now more or less obsolete (with one or two notable exceptions), but in their heyday, they were critical to the design of many electronic systems, from radios to telephones to computers. In this article, we’ll take a look at how vacuum tubes work, why they went away, and why they didn’t go away entirely.
Thermionic Emission / 热离子发射
真空管的基本工作原理是一种叫做热电子发射的现象。它的工作原理是这样的：加热金属，热能将一些电子击散。1904 年，英国物理学家约翰-安布罗斯-弗莱明（John Ambrose Fleming）利用这种效应制造出第一个真空管设备，他称之为振荡阀。
The basic working principle of a vacuum tube is a phenomenon called thermionic emission. It works like this: you heat up a metal, and the thermal energy knocks some electrons loose. In 1904, English physicist John Ambrose Fleming took advantage of this effect to create the first vacuum tube device, which he called an oscillation valve.
弗莱明的装置由两个电极组成，即阴极和阳极，分别置于封装玻璃管的两端。当阴极被加热时，它会通过热电子发射放出电子。然后，在阳极（也称为极板）上施加正电压，这些电子就会被吸引到极板上，并流过间隙。将电子管中的空气抽走形成真空，电子就有了从阴极到阳极的畅通路径，从而产生电流。
Fleming’s device consisted of two electrodes, a cathode and an anode, placed on either end of an encapsulated glass tube. When the cathode is heated, it gives off electrons via thermionic emission. Then, by applying a positive voltage to the anode (also called the plate), these electrons are attracted to the plate and can flow across the gap. By removing the air from the tube to create a vacuum, the electrons have a clear path from the cathode to the anode, and a current is created.
A simplified diagram of a vacuum tube diode. When the cathode is heated, and a positive voltage is applied to the anode, electrons can flow from the cathode to the anode. Note: A separate power source (not shown) is required to heat the cathode.
真空管二极管简图。当阴极被加热，阳极被施加正电压时，电子就会从阴极流向阳极。注：加热阴极需要一个单独的电源（未显示）。
这种只有两个电极的真空管被称为二极管。二极管一词至今仍被用来指只允许电流单向流动的电子元件，尽管如今这些设备都是以半导体为基础的。就真空管二极管而言，电流只能从阳极流向阴极（尽管电子从阴极流向阳极，但请记住，传统电流的方向与电子的实际运动方向相反--这是电气工程史上令人讨厌的遗留问题）。二极管通常用于整流，即从交流电（AC）转换为直流电（DC）。
This type of vacuum tube, consisting of only two electrodes, is called a diode. The term diode is still used today to refer to an electrical component that only allows an electric current to flow in one direction, although today these devices are all semiconductor based. In the case of the vacuum tube diode, a current can only flow from the anode to the cathode (though the electrons flow from the cathode to the anode, recall that the direction of conventional current is opposite to the actual movement of electrons—an annoying holdover from electrical engineering history). Diodes are commonly used for rectification, that is, converting from an alternating current (AC) to a direct current (DC).
真空管二极管更逼真的示意图。电极在真空管内排列成同心圆柱状，使电子的表面积最大化。在这里，阴极由单独的加热丝加热，标注为 “加热器”。(图片由维基百科用户 Svjo 提供）。
A more realistic representation of a vacuum tube diode. The electrodes are arranged as concentric cylinders within the tube, maximizing the surface area for electrons. Here, the cathode is heated by a separate heating filament, labeled Heater. (Image courtesy of Wikipedia user Svjo.)
Third Electrode’s the Charm
虽然二极管是一种非常方便的设备，但它并没有为真空管的功能设定极限。1907 年，美国发明家李-德-弗雷斯特（Lee de Forest）在其中加入了第三个电极，创造了第一个三极管。这第三个电极被称为控制栅，它使真空管不仅可以用作整流器，还可以用作电信号放大器。
While diodes are quite a handy device to have around, they did not set the limit for vacuum tube functionality. In 1907, American inventor Lee de Forest added a third electrode to the mix, creating the first triode tube. This third electrode, called the control grid, enabled the vacuum tube to be used not just as a rectifier, but as an amplifier of electrical signals.
控制栅位于阴极和阳极之间，呈网状（孔洞允许电子通过）。通过调节施加在控制栅上的电压，可以控制从阴极流向阳极的电子数量。如果给栅极施加较强的负电压，它就会排斥来自阴极的电子，阻断电流的流动。栅极电压越高，通过它的电子就越多，电流也就越大。这样，三极管就可以充当电流的开关和信号放大器。
The control grid is placed between the cathode and anode, and is in the shape of a mesh (the holes allow electrons to pass through it). By adjusting the voltage applied to the grid, you can control the number of electrons flowing from the cathode to the anode. If the grid is given a strong negative voltage, it repels the electrons from the cathode and chokes the flow of current. The more you increase the grid voltage, the more electrons can pass through it, and the higher your current. In this way, the triode can serve as an on/off switch for an electrical current, as well as a signal amplifier.
A simplified diagram of a vacuum tube triode. A minute adjustment to the grid voltage has a comparatively large effect on the plate current, allowing the triode to be used for amplification.
真空管三极管简化图。对栅极电压的微小调整就会对极板电流产生比较大的影响，从而使三极管可以用于放大。
三极管可用于放大信号，因为控制栅电压的微小变化会导致极板电流的巨大变化。这样，栅极上的小信号（如无线电波）就能在极板上转换成波形完全相同的大信号。请注意，您也可以通过增加板极电压来增大板极电流，但要达到同样的电流放大效果，您必须改变板极电压的幅度大于栅极电压。
The triode is useful for amplifying signals because a small change in the control grid voltage leads to a large change in the plate current. In this way, a small signal at the grid (like a radio wave) can be converted into a much larger signal, with the same exact waveform, at the plate. Note that you could also increase the plate current by increasing the plate voltage, but you’d have to change it by a greater amount than the grid voltage to achieve the same amplification of current.
The original triode vacuum tube, the Audion, invented by Lee de Forest in 1906. (Image courtesy of Gregory F. Maxwell.)
最初的三极管真空管 Audion，由 Lee de Forest 于 1906 年发明。(图片由 Gregory F. Maxwell 提供）。
三极管真空管的演变，从 1916 年的型号（左）到 20 世纪 60 年代的型号。(图片由维基百科用户 RJB1 提供）。
The evolution of triode vacuum tubes from a 1916 model (left) to one from the 1960s. (Image courtesy of Wikipedia user RJB1.)
但是，既然可以有四个电极，为什么只停留在三个电极上呢？或者五个？真空管的进一步改进将一个附加栅格（称为屏蔽栅格）和另一个附加栅格（称为抑制栅格）置于更靠近阳极的位置，从而形成了一种分别称为四极管和五极管的真空管。这些额外的栅格解决了一些稳定性问题，并解决了三极管设计的其他局限性，但功能基本保持不变。
But why stop at three electrodes when you could have four? Or five, for that matter? Further enhancements of vacuum tubes placed an additional grid (called the screen grid) and yet another (called the suppressor grid) even closer to the anode, creating a type of vacuum tube called a tetrode and a pentode, respectively. These extra grids solve some stability problems and address other limitations with the triode design, but the function remains largely the same.
The Transistor Is Born, but the Tube Lives On
1947 年第一台晶体管的复制品。
A replica of the first transistor created in 1947.
1947 年，物理学家威廉-肖克利、沃尔特-布拉坦和约翰-巴丁三人创造了世界上第一个晶体管，标志着真空管终结的开始。晶体管可以复制电子管的所有功能，如开关和放大，但它是由半导体材料制成的。
In 1947, the trio of physicists William Shockley, Walter Brattain and John Bardeen created the world’s first transistor, and marked the beginning of the end for the vacuum tube. The transistor could replicate all the functions of tubes, like switching and amplification, but was made out of semiconductor materials.
晶体管一经问世，除了最特殊的应用外，真空管便开始走向消亡。晶体管更加耐用（真空管就像灯泡一样，最终需要更换），体积更小（想象一下在 iPhone 中安装 20 亿个真空管的情景），而且比真空管需要更低的电压才能工作（晶体管没有需要加热的灯丝）。
Once the transistor cat was let out of the bag, vacuum tubes were on their way to extinction in all but the most specific of applications. Transistors are much more durable (vacuum tubes, like light bulbs, will eventually need to be replaced), much smaller (imagine fitting 2 billion tubes inside an iPhone), and require much less voltage than tubes in order to function (for one thing, transistors don’t have a filament that needs heating).
尽管出现了晶体管，但真空管并没有完全消亡，它们在一些特殊应用中仍然有用。例如，真空管仍然用于高功率射频发射机，因为它们可以产生比现代半导体同类产品更大的功率。因此，在粒子加速器、核磁共振扫描仪甚至微波炉中都能看到真空管的身影。
Despite the emergence of the transistor, vacuum tubes aren’t completely extinct, and they remain useful in a handful of niche applications. For example, vacuum tubes are still used in high power RF transmitters, as they can generate more power than modern semiconductor equivalents. For this reason, you’ll find vacuum tubes in particle accelerators, MRI scanners, and even microwave ovens.
不过，真空管在现代音乐界的应用可能最具魅力。发烧友们对真空管放大器的品质信誓旦旦，相比半导体放大器，他们更喜欢真空管放大器的声音，而许多专业音乐家也不会考虑使用任何东西来代替真空管放大器。这种偏好是否有道理尚存争议，但您可以在这篇详尽的 IEEE Spectrum 文章中深入了解真空管声音的迷人世界。
But perhaps the most charming modern application of vacuum tubes is in the musical community. Audiophiles swear by the quality of vacuum tube amplifiers, preferring their sound to semiconductor amps, and many professional musicians won’t consider using anything in their place. Whether there’s any merit to this preference is a matter of some debate, but you can dive more into the fascinating world of tube sound in this thorough IEEE Spectrum article. ( Vacuum Tube Amps: Origins, Advantages, and Audio Uses - IEEE Spectrum)
现代吉他放大器中使用的真空管
Vacuum tubes being used in a modern guitar amplifier.
真空管曾经辉煌过，而现在世界的动力来自晶体管。但电子技术的未来会怎样？摩尔定律已经达到极限，量子计算也在地平线上若隐若现，技术进步的浪潮将把我们带向何方，谁也说不准。
Vacuum tubes had their day, and now the world is powered by transistors. But what does the future hold for electronics? With Moore’s Law reaching its limits, and quantum computing looming tantalizingly on the horizon, it’s anybody’s guess where the wave of technological advancement will bring us next.
参考：
Vacuum Tubes: The World Before Transistors - Engineering.com
真空管又称阀门，是一种用于控制被抽真空空间隔开的电极之间的高真空电流的装置。在整个 20 世纪上半叶，它们都是电子电路中的基本元件。二极管是真空管的最简单形式，由约翰-安布罗斯-弗莱明于 1904 年发明。它由一个阴极和一个阳极组成，电子从阴极移动到阳极。真空管对无线电、电视和早期计算机等技术的发展至关重要，直到 20 世纪中期才被晶体管等半导体器件所取代。
Vacuum tubes, also known as valves, are devices used to control electric current in a high vacuum between electrodes separated by an evacuated space. These were fundamental components in electronic circuits throughout the first half of the 20th century. The simplest form of a vacuum tube is the diode, which was invented in 1904 by John Ambrose Fleming. It consists of a cathode and an anode, with electrons moving from the cathode to the anode. Vacuum tubes were essential for the development of technologies like radio, television, and early computers until they were largely replaced by semiconductor devices like transistors in the mid-20th century.
Types and Functions of Vacuum Tubes
真空管有多种类型，每种类型都是为特定应用而设计的。例如，热离子管或热离子阀利用热阴极的热离子发射来实现信号放大和电流整流等电子功能。其他类型的真空管，如真空光电管，则通过光电效应利用电子发射来检测光强度。真空管可根据有源电极的数量进行分类，常见的类型有二极管、三极管、四极管和五极管，每种类型都具有不同的功能，如放大、整流或开关。
There are various types of vacuum tubes, each designed for specific applications. For instance, the thermionic tube or thermionic valve uses thermionic emission from a hot cathode to achieve electronic functions like signal amplification and current rectification. Other types, like vacuum phototubes, use electron emission through the photoelectric effect for detecting light intensities. Vacuum tubes can be classified based on the number of active electrodes, with diodes, triodes, tetrodes, and pentodes being common types, each serving different purposes like amplification, rectification, or switching.
Triodes and Their Role
三极管是一种真空管，包括三个电极：阴极、阳极和控制栅。控制栅通过调节从阴极到阳极的电子流，使三极管发挥电子放大器的功能。李-德-弗雷斯特于 1907 年发明了三极管，它通过提供电子放大功能，在长途电话和无线电通信的发展中发挥了至关重要的作用。三极管的工作原理是利用施加在控制栅上的电压来控制阴极和阳极之间的电流，从而实现早期电子设备的信号处理。
Triodes are a type of vacuum tube that includes three electrodes: the cathode, anode, and a control grid. The control grid enables the triode to function as an electronic amplifier by regulating the electron flow from the cathode to the anode. Lee de Forest invented the triode tube in 1907, and it played a critical role in the development of long-distance telephony and radio communication by providing electronic amplification. Triodes operate by using the voltage applied to the control grid to control the current between the cathode and the anode, which enables signal processing in early electronic devices.
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