|
UNIT 6
Task 1. Study new words and word combinations.
1
|
vacuum valve
|
['vækjuːm]
|
вакуумная лампа
|
2
|
perform a function
|
['fʌŋkʃ(ə)n]
|
выполнять функцию
|
3
|
indispensable
|
[ˌɪndɪ'spen(t)səbl]
|
важный, необходимый
|
4
|
radar
|
['reɪdɑː]
|
радар
|
5
|
equipment
|
[ɪ'kwɪpmənt]
|
оборудование
|
6
|
drawback
|
['drɔːbæk]
|
недостаток
|
7
|
waste
|
[weɪst]
|
тратить впустую
|
8
|
heat
|
[hiːt]
|
нагрев, нагревать
|
9
|
require
|
[rɪ'kwaɪə]
|
требовать
|
10
|
amplification
|
[ˌæmplɪfɪ'keɪʃn]
|
усиление
|
11
|
dimension
|
[daɪ'menʃn]
|
размер
|
12
|
radiant
|
['reɪdɪənt]
|
излучающий
|
13
|
sensitive to
|
['sensɪtɪv]
|
чувствительный к
|
14
|
admixture
|
[əd'mɪksʧə]
|
примесь
|
15
|
particle
|
['pɑːtɪkl]
|
частица
|
16
|
pressure
|
['preʃə]
|
давление
|
17
|
junction
|
['ʤʌŋkʃən]
|
соединение, переход
|
18
|
emitter
|
[i'mitər]
|
эмиттер, излучатель
|
19
|
power amplifier
|
|
усилитель мощности
|
20
|
dopant
|
['dəupənt]
|
легирующая примесь
|
21
|
obtain
|
[əb'teɪn]
|
получать, приобретать
|
TASK 2. Read the text below and translate it.
TRANSISTORS
Before the invention of transistors electronic (vacuum) valves were used to perform these functions. Electronic valves are wonderful devices. Besides their indispensable use in radio and television sets, they do many other jobs. They are used in radar and motion-picture equipment. They are basic elements in “electronic brains”. But electronic valves have several drawbacks. They waste a good deal of electricity. One of the elements in a vacuum valve must be heated so that it will give off electrons. This heating requires electricity and produces unwanted heat that needs special cooling equipment to get rid of this heat.
The transistor is a semiconductor device for the amplification of electric signals. The application of transistors instead of electronic valves made it possible to design compact, small-dimension electronic devices, which consume very little power. The transistors are successfully used for direct transformation of heat energy into electrical energy by means of thermal elements. They are widely used to transform radiant energy into electricity with the help of photocells, or so-called solar batteries. Light sources and lasers are also built on the basis of transistors.
Transistors are extremely sensitive to external influences. Even thousandths of one per cent of admixtures change their electrical conductive properties by hundreds of thousands of times. They are very sensitive to the action of light, nuclear particles, pressure, etc.
Transistors are made of small germanium crystals. Germanium is an element crystalline in form. Germanium crystal used in a typical transistor may be much less than 1/8 inch square and less than 1/32 inch thick. There are different types of transistors in use, and still more are being developed. A very fine technology has been developed for obtaining transistors with pre-set physical properties by introducing into them admixtures of gold, copper, nickel, zinc. The transistor of great importance at present is the junction-type triode. This transistor contains three distinct regions of semiconductor, each having ohmic lead. One of the junctions is called the emitter, the other one — the collector. This transistor is a power amplifier.
Transistors nowadays are made of silicon too. Silicon is neither a good conductor nor a good insulator – that's why it, and other solids such as germanium, are known as semiconductors. As a semiconductor, silicon is very sensitive to impurities — these are called dopants. If you add as little as 0.0001% of a dopant to silicon, you can increase conductivity by 1000 times. The transistor consists of two types of silicon. One type has been doped with boron which gives it a positive charge – this is termed p-type silicon. The other type has been doped with phosphorus which gives it a negative charge -this is known as n-type silicon. By doping a silicon crystal with p and n type dopants a p-n junction is formed.
Transistors revolutionized radio engineering and electronics. Because of their small size, the absence of incandescence and other properties, transistors make it possible to produce devices which cannot be made with vacuum tubes.
TASK 3. Answer the following questions and retell the text.
1. What is the most common element on this planet? 2. Why is it important to use silicon? 3. Why is polythene used for insulation? 4. Is silicon an insulator or a conductor? 5. How are impurities called? 6. What can you do by doping impurities to a semiconductor? 7. What types of semiconductors can be formed by doping impurities? 8. What is a p-n junction?
Do'stlaringiz bilan baham: |
