工程师 - 真空管(Vacuum tubes)

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