Учебное пособие предназначено для бакалавров всех специальностей и направлений подготовки радиотехнического факультета. В нем представлены материалы для аудиторной и самостоятельной работы
 Скачать 1.03 Mb.
|
UNIT 6Task 1. Study new words and word combinations.
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? TASK 4. Choose the correct answer according to the text. According to the text, what is the best element for transistor production? oxygen silicon copper According to the text, polythene is resistant to electricity and it is used for insulating. making electric cable. regulating the current flow. Which of these materials is not the material of very low resistance? germanium copper iron Which of these characteristics is not common for silicon? It is solid. If has the ability to conduct electricity. If is often used as an insulator. “dopants” are elements, which are resistant to electricity. impurities, to which silicon is very sensitive. the most common elements on the Earth. TASK 5. Find the words opposite in meaning. Solid, bottom, right, liquid, insulator, top, increase, positive, drop, high, left, little, conductor, negative, much, low. TASK 6. Translate the words, pay attention to the suffixes. resist, resistance, resistant insulate, insulation, insulator, insulated, insulating conduct, conductor, conductivity, conductance, conduction, conductive electricity, electric, electrician, electrify, electrical TASK 7. Change the sentences from active into passive. Nowadays people use silicon to produce transistors. Nowadays silicon… Usually we insulate copper wire with polythene. Usually copper wire… We use iron and copper for making electric cable. Electric cable… You can increase conductivity of silicon by adding a dopant to it. Conductivity of silicon… You can form a p-n junction by doping a silicon crystal with p and n type dopants. P-n junction… Professor applied a voltage to one of the contacts to show us the work of the p-n junction. A voltage… TASK 8. Fill in the gaps with the following prepositions: to, with, of, on, in, through, at, into A semiconductor chip is a tiny board made … silicon and germanium. 2. All elements can be divided … three groups; the first group includes the elements resistant ... electricity; the second one includes the elements … low resistance; and the last one includes semiconductors. 3. He said that it would be better to insulate this piece of copper wire … polythene. 4. If we look … the scheme of a p-n-p junction we can see that … the right there is an emitter, … the left there is a collector and … the middle you can see a base. 5. Compass is a device which is very sensitive … the magnetic field of the earth. 6. Each layer of semiconducting material is doped … a small amount of impurity. 7. You should connect each of the two parts of the system … separate sources of power. 8. This method can be applied … the production of new electronic devices. 9. Let’s look at the Mendeleyev Periodic Table of elements. Such elements as hydrogen, oxygen, carbon and nitrogen are placed … the top of table and such elements as lead, gold, mercury are … the bottom of it. 10. They say that current flows … a vacuum in only one direction. TASK 9. Match the words with their meanings.
TASK 10. Listen to the recording and fill in the gaps. CHANGE OF STATE Many 1) … can exist in more than one state – as a 2)…, 3) …, or gas. Which state they are in 4) … their temperature and 5) …. At certain temperatures, under normal atmospheric pressure, some substances 6) … state. Liquids, for example, may become solids or 7) …, and gases may condense into liquids. Elements change state, under normal pressure, at specific temperatures, known as 8) … (or freezing) and 9) … (or condensation) points. TASK 11. Watch the video about the working principle of MOSFET transistor and answer the questions. 1. What does MOSFET stand for? 2. What kind of a substrate is shown in the video? 3. What are white and green colors used to show? 4. What is red color used to show? 5. What is used to produce an insulating layer? 6. What is applied above the insulating layer? 7. What elements does the MOSFET shown in the video consist of? 8. Which two elements share the same source of current? 9. How can we increase the current between source and drain? 10. Where are MOSFETS used? |