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Transistors and Semiconductor Devices
1. Devices consisting of solid pieces of crystalline material which allowed alternating current to flow more readily in one direction than the other were known long before the invention of the thermionic valve. The crystal set1 which became so well known in the early days of radio depended on the rectifying action at the point of contact between the surface of certain crystals and a fine wire. Crystal valves2, using silicon crystals, were found to be more efficient for the very high frequency signals reaching radar receivers than any thermionic valves. The action of these devices was not understood, but they were all made from materials which we now classify as semiconductors: substances which let electric current pass through them more easily than insulators do but much less easily than do true conductors. These semiconductor devices were used as rectifiers although by 1924 a scientific worker at the laboratory headed by Bonch-Bruyevich in Nizhni Novgorod Oleg Losev for the first time in the history of electronics had achieved amplification using a semiconductor crystal. Unfortunately, Losev's discovery did not receive due attention.
2. In 1948 Bardeen and Brattain invented the point-contact transistor and Shockley invented the junction transistor shortly after. The transistor is a semiconductor triode possessing characteristics which are similar in many respects to those of thermionic triodes. At present transistors are widely used in amplifiers, receivers, transmitters, oscillators, TV sets, measuring instruments, pulse circuits, computers, and many other types of radio equipment.
3.The invention of transistors and solid-state devices led to an acceleration in the growth of electronics. Why were these new devices so important and why are they steadily replacing their older equivalents? A brief review of their advantages compared with thermionic devices will provide the answers to these questions. Transistors are made from parts which do not wear out. Transistors waste very little power. They require no heating to generate their free electrons. This means that equipment made with transistors is more efficient, lighter than comparable valve equipment.
4. Since no heating is required there is no delay in transistor equipment waiting for things to warm up, as there is with thermionic valves. This is a great advantage with 'entertainment' equipment, such as radio and television receivers, and it may be vital with some kinds of measuring or recording equipment.
5. Their very small size and weight, combined with low heat dissipation3, permits very high density packing of components and, in combination with their reliability, this has made possible the design of the very compact circuits which are essential for such applications as computers, portable measuring instruments, satellite instrumentation, etc.
1.crystal set – детекторный приемник
2.crystal valve – кристаллический прибор
3.heat dissipation – рассеяние тепла
II. Say whether the following statements are true or false:
1. Devices consisting of crystalline materials were known long before the invention of the thermionic valve. 2. The crystal set became known in the early days of radio. 3. Crystal valves were found to be less efficient rectifiers than thermionic valves. 4. The action of semiconductor devices was understood well.
III. Answer the following questions on paragraph 2:
1. What is a transistor? 2. When was the first transistor invented? 3. Where are transistors used?
IV. In paragraph 3 find the English equivalents of the following words:
транзистор, твердотельный прибор, ускорение, рост, прибор, заменять, неуклонно, краткий, преимущество, сравнивать, давать ответы.
V. Translate paragraph 4.
VI.Read paragraph 5 and say where the small size and weight of transistors is essential.
VII.Write out of the text the words and phrases describing the transistor.
VIII.Divide text A into logical parts and find the topical sentence of each part.
IX. Tell the story of transistors and semiconductor devices using the topical sentences.
I. Look through the list of English words and their Russian equivalents facilitating reading text B:
integrated circuit – интегральная схема; resistor – резистор; capacitor – конденсатор, емкость; package, case – корпус; lead – ввод, вывод; infinitesimally small terms – бесконечно малые члены выражения; chip (die) – чип, кристаллик; to tend – иметь тенденцию; cost – цена, стоимость; common – широко распространенный; общепринятый; thin– and thick-film ICs – тонко пленочные и толстопленочные интегральные схемы (ИС); simultaneously – 1. одновременно; 2. совместно; complete – полный, завершенный; performance – 1. производительность; эффективность; 2. качество функционирования; digital computer – цифровая ЭВМ; design – 1. проект; 2. конструкция; to design – проектировать, конструировать, разрабатывать; evaluate – оценивать; to bring about – вызывать, быть причиной.
II. Skim through the text and say what it is about (you are given 10 minutes):
An integrated circuit (IС) is a collection of interconnected transistors, diodes, resistors, and capacitors mounted in one package or case with as many as fourteen leads.
The word "integrated" does not refer to the mathematical process of adding together an infinite number of infinitesimally small terms, but rather to the fact that all transistors, diodes, and resistors are formed from a single piece of semiconductor material called a "chip" or a "die". If only one chip is present in the case, the IС is called "monolithic"; if several chips are mounted inside the case the IС is called "hybrid". Some integrated circuits contain several thousand transistors and resistors, and so extreme miniaturization is possible.
Because of their extremely small size, integrated circuits tend to be restricted to low power applications. Their small size, however, does enable them to operate at high frequencies. The cost of an IС is considerably less than the total cost of the separate components.
Monolithic ICs are by far the most common, but there are other kinds. Thin-film and thick-film ICs are larger than monolithic ICs but smaller than discrete circuits. With a thin– or thick-film IС, the passive components like resistors and capacitors are integrated simultaneously on a substrate. Then, discrete active components like transistors and diodes are connected to form a complete circuit. Therefore, commercially available thin– and thick-film circuits are combinations of integrated and discrete components1.
If only a few components have been integrated to form the complete circuit it is an example of small-scale integration (SSI)2. As a guide, SSI refers to ICs with less than 12 integrated components.
Medium-scale integration (MSI)3 refers to ICs that have from 12 to 100 integrated components per chip. Large-scale integration (LSI)4 refers to more than a hundred components.
The IС is becoming more important as a component to be used in the design of electronic equipment, not only in equipment that must be small and light in weight, but where reliability and performance are demanded. In many areas of application particularly in digital computers, the IС provides more economical designs.
A number of important new developments are being evaluated both in the laboratory and in limited product usage. Some of these promise to bring about significant changes in the way microcircuits are designed and used.
1.discrete component – дискретный компонент
2.SSI (small-scale integration) – малая интегральная схема
3.MSI (medium-scale integration) – средняя интегральная схема
4.LSI (large-scale integration) – большая интегральная схема
III. Answer the following questions:
1. What is an integrated circuit? 2. What does the word 'integrated' mean? 3. What types of integrated circuits are known to you? 4. What is large scale integration?
IV. Give the main points of text В in 3-5 sentences.
V.Speak about integrated circuits.
I.Look through the list of English words and their Russian equivalents. You will need them for better understanding text C:
reduction – уменьшение, сокращение; bulky electronic equipment – громоздкое электронное оборудование; printed circuit – печатная схема; trend – общее направление, тенденция; to reduce – уменьшать, сокращать; to consume – потреблять, расходовать; durable – долговечный, прочный; coating – покрытие; lattice – (кристаллическая) решетка; to assemble – собирать, монтировать; to look ahead – смотреть вперед, смотреть в будущее; packing density – плотность монтажа; плотность упаковки; unit – устройство; узел; блок; прибор; tremendous – громадный, огромный; diverse – разный; molecular electronics – молекулярная электроника.
II.Scan text С and find the answers to the following questions:
1.What is a major trend in modern radio electronics?
2.What possibilities does molecular electronics open up?
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