Vacuum Tubes

1. The science of electronics now deals almost exclusively with transistors and other solid-state devices. However, vacuum tubes were the principal building blocks¹ of electronic circuits until approximately 1955. Briefly, a vacuum tube .consists of several metal electrodes of various shapes all packaged inside a glass or metal envelope² which is highly evacuated. Vacuum tubes are often called thermionic "valves". A red hot metallic electrode (the filament or cathode) emits electrons which are attracted to a positively charged electrode called the plate or anode. The electrons pass through the spaces in a metallic grid electrode on their way to the plate, and the voltage on the grid controls how many electrons reach the plate. A simple thermionic valve is called a diode because it has two electrodes. A triode is a valve with three electrodes, an anode, a cathode and a control grid. A tetrode has four, and a pentode – five electrodes.

2. Vacuum tubes are still used in oscilloscopes, television sets, high power high frequency radio transmitters, and in some special low noise amplifiers. However, every year sees a larger number of applications being transistorized. It is probably safe to say that this trend will continue in the future, as there is presently a great deal of technological development being put into solid state electronics and rather little put into vacuum tube electronics.

3. As a general rule, vacuum tubes are inferior to modern solid state devices³ in many ways. Vacuum tubes are much larger. They require considerably more electric power to operate. However, they can handle high voltages and high powers⁴ at high frequencies somewhat more easily than solid state devices. They are also capable of withstanding temporary overloads⁵ in voltage or current which would permanently destroy⁶ a solid state device and then returning to normal operation.

Notes

1. principal building blocks – основные стандартные блоки

2. packaged inside an envelope – заключенный в баллон

3. inferior to modern solid state devices – уступают современным твердотельным приборам

4. to handle high voltages and high powers – оперировать высоким напряжением и высокой мощностью

5. to withstand temporary overloads – выдерживать временные перегрузки

6.would permanently destroy – неизменно разрушает

III. Say what principal blocks electronic circuits were made of before 1955.

IV.Give reasons for replacing vacuum tubes by transistor devices.

V.Which paragraph contains the information directly connected with the title of the text. Render this information to your partner.

VI.Imagine that you are to make a report on the theme "The Age of Electronics". Use the information of all three texts А, В and С. The following plan will help you:

1. The discovery of the electron.

2. The revolution in pure science.

3. The revolution in technology.

4.General uses of electronics.