metodIII

Unit 3

I. Practice the pronunciation of the following words and word combinations:

Lowly diode, apt, junction, deficiency, carrier, depletion, biased, tremendous, neutralize, vacant, amplifier, similarly, bipolar, vary, volume, surpass, barren, pour.

II. Memorize the words and word-combinations:

The Junction Transistor

To understand how a transistor works, first consider the lowly diode. It is a simple union of the two most fundamental kinds of semiconductor, known as n- type and p-type. Both conduct current, but the n-type does it with electrons, while the p-type depends on electron deficiencies, better known as holes. Joining these two types of semiconductors forms what is known as a p-n junction at their boundary. This is the core of a semiconductor diode, which conducts current in one direction.

Connect a battery's positive terminal to the n-type material and electrons are attracted to that terminal, while holes in the p-type material move toward the negative terminal. In other words, charge carriers stream away from the junction, expanding a barren volume, aptly called the depletion region. The diode is said to be reverse-biased and hardly any current flows.

Now reverse the battery connections. Electrons in the n-type material move toward the junction and are constantly replenished by the battery. Meanwhile, holes in the p-type material stream toward the junction, repelled by the positive battery terminal. The depletion region shrinks tremendously as holes and electrons combine at the junction, neutralizing one another, as more stream in on either side from the battery. The diode is said to be forward-biased; current flows easily. Thus, a diode can control the direction of current, but not how large it is.

A transistor, on the other hand, can control how much current goes through it and also act as an amplifier. The simplest transistor has three parts: an emitter, a base, and a collector. Think of the transistor as a sandwich of two p-n junctions back to back in either n-p-n or p-n-p order; they operate similarly.

In an n-p-n transistor, for example, the n-type emitter has many extra electrons, the relatively thin p-type base has a small number of holes, and the n-type collector has a moderate number of electrons. (Junction transistors are also known as bipolar devices because, in the emitter, holes and electrons flow in opposite directions). A transistor amplifier takes a small, varying voltage – an input signal – between the base and the emitter, and uses it to control a larger current flowing from the emitter to the collector. That's the output. The key agents in this amplification are the depletion regions. With two p-n junctions in the device, there are two depletion regions: one between the emitter and the base, the other between the base and the collector.

First, the emitter-base diode is forward-biased by a voltage source. Electrons flow from the emitter into the base. The base-collector diode, on the other hand, is reverse-biased, so that holes will not flow into the base, which would intercept any electrons coming across from the emitter and therefore block current from flowing through the device.

With this setup, the current through the transistor, from emitter to collector, is controlled by the depletion region around the emitter-base junction. When it is thick, the current is choked off; when it is thin, lots of current flows through the device. But hold on – when it is thin, and electrons shoot across the emitter-base junction, aren't they blocked by the fat depletion region around the base-collector junction? No – the base is narrow, so the momentum of the electrons pouring in from the emitter brings them close to that junction. From there, the positive voltage at the junction then sweeps most of the electrons into the collector. Only a few are lost in the base as they move into the vacant holes.

The transistor is designed so that the flow of electrons from emitter to collector is very sensitive to the current into the base. This is done by making the base very thin (so electrons don't have far to go before reaching the collector) and using low doping (electrons cannot easily find vacant holes to fill). The voltage across the

base-emitter junction provides the electric field that drives electrons from the base into the collector.

With the emitter-base junction forward-biased, a varying voltage put on top of it

– an input signal – varies the depletion region, which in turn varies a relatively large current flowing through the device. Add a load resistor in the collector circuit, and that small varying input produces a much larger varying collector voltage: the transistor amplifies the signal at the base. Depending on the circuit, the result will be current, voltage, or power amplification.

Although bipolar junction transistors have been surpassed for many applications by various forms of field-effect transistors, bipolars remain popular for applications involving high-frequency signals. They're found in countless modern electronic devices, including broadband Internet modems, set-top boxes, DVD players, and CD-ROMs.

Vocabulary, Comprehension and Summary Writing

I. Answer the following questions to check your understanding the text:

1.What is a simple union of two most fundamental kinds of semiconductor?

2.How do they conduct current?

3.What forms p-n junction?

4.When do charge carriers steam away from the junction?

5.What is depletion region?

6.What does reverse-biased diode represent?

7.To what do electrons move in n-type material?

8.What can you say about holes in p-type materials?

9.What happens to the depletion region?

10.How is the diode called in this respect?

11.Does the diode control the direction of current?

12.What about a transistor? How does it act?

13.What does simplest transistor consists of?

14.How can you imagine an n-p-n transistor?

15.Why are junction transistors known as bipolar devices?

16.For what purpose does a transistor amplifier use varying voltage?

17.What is the key agent in this amplification?

18.Due to what are two depletion regions created?

19.What makes the emitter-base diode be forward-biased?

20.What about base-collector diode?

21.What does the depletion region control around the emitter-base junction?

22.What can you say about the design of transistor?

23.For what do bipolar transistors remain popular?

II. Write a list of keywords to the text.

III. Translate the following sentences. Be sure that you know the meaning of these words.

Like, unlike, likely (is likely to…), unlikely (is unlikely to…).

1.Like charges repel and like charges attract each other.

2.A transistor unlike to a diode can control how mach current goes through it and also acts as an amplifier.

3.These two devices are unlikely to operate similarly.

4.With this setup, the current through the transistor is likely to be controlled by the depletion region around the emitter-base junction.

5.Transistor and diode unlike to the relay and manual switch offer less impedance to the flow of current when turned off and have a large forward voltage when turned on.

6.The above circuits are likely to perform operations which are often referred to as “logic circuits”.

7.Combinations of these binary digits is unlikely to represent decimal numbers.

IV. From the following choose the word that is most nearly the same in meaning to the bold one:

convent – convey, transform, enter, control; concept – abstract notion, understanding, collection; conduct – give, collect, carry on, design;

certain – doubtful, changeable, various, sure; destroy – repair, ruin, separate, develop; provide – depend, amplify, vary, supply.

V.State the difference between the terms:

1.n-type and p-type semiconductors;

2.n-p-n and p-n-p order of junction;

3.the emitter-base diode and the base collector diode.

VI. Give terms that correspond to the following bold word combination.

1.Such diode is forward-biased by a voltage source.

2.The n-type emitter has many extra electrons in this transistor.

3.There are two depletion regions with these two kinds of junctions.

4.This type of semiconductor depends on electron deficiencies, better known as holes.

VII. Choose words from the text to fill in the blanks.

1.We can imagine the transistor as ….. of two ….. back to back in either n-p-n or p-n-p order.

2.If a battery’s positive terminal connected to the n-type material electrons ….. to that terminal.

3.….. are found wide application in countless modern electronic devices including broadband Internet modems, DVD players, and so on.

1.Коли був винайдений транзистор? (Транзистор був винайдений у 1948

р.)

2.Які переваги транзистора в порівнянні з елетронно-вакуумною лампою? (Транзистор значно менше ніж вакуумна лампа, дешевше, більш надійний і споживає менше енергії.)

3.Чи набагато зменшились фізичні розміри пасивних елементів? (Так, пасивні елементи, такі як резистори, конденсатори та котушки індуктивності значно зменшені у розмірах шляхом використання нових матеріалів і технологій.)

4.Від чого залежить робота транзистора? (Робота транзистора залежить від явищ, що проходять в переході між p- та n- типами матеріалу.)

5.Що являє собою напівпровідниковий перехід? (Напівпровідниковий перехід являє собою зміну від p- до n- типу матеріалу в одній і тій самій суцільний кристалічній решітці.)

6.Що називають збідненим шаром? (Шар, в якому область переходу відносно вільна від дірок та вільних електронів в результаті першопочаткової міграції, називається збідненим шаром.)

7.Що нагадує дія базо-емітерного переходу при прямому зміщенні? (Дія база-емітерного переходу при прямому зміщенні нагадує відкривання воріт і дозволяє струму проходити до колекторно-емітерного ланцюга. В цьому і полягає сутність роботи транзистора.)

XII. Learn to write summaries. Follow the algorithm given below:

Step I: Read the text twice and state its subject-matter.

a)Identify keywords related to the subject-matter.

b)Use these words in key sentences.

Step II: State the aim of the text.

a)Find the information about author’s intentions.

b)State the aim of the text in a single sentence. Step III: Identify the main ideas (factual information).

a)Identify the key parts of the text.

b)Separate the author’s own ideas and arguments (original factual

information) from the information he is simply presenting.

c) Omit secondary (supporting) facts and describe the main ideas contained in publication

Step IV: Identify conclusions the author draw in his paper.

Some words and phrases commonly used to describe objective of the article: The paper deals with …, the article describes …, the book is devoted to …, the

subject-matter of the paper is …, the review discusses …, the article is aimed at …, the author’s intention is …, thus …, therefore …, consequently …, in summary …, data obtained give every reason to suggest …, the following conclusion can be drawn.

XIII. Read the text, given below, twice. Write summaries using mentioned above proposed algorithm, words and phrases.

From the history of the Transistors

Working at Bell Labs in 1947 John Barden and Walter Brattain were trying to understand the nature of the electrons in the interface between metal and a semiconductor. They realized that by making two point contacts very close to one another, they could make a three terminal device – the first “point contact” transistor. Then they quickly made a few of these transistors and connected them with some other components to make an audio amplifier. This audio amplifier was shown to chief executives at Bell Telephone Company, who were very impressed that it didn’t need time “to warm up” (unlike to the heaters in the vacuum tube circuits). They immediately realized the power of this new technology.

This invention was the spark that ignited a huge research effort in solid-state electronics. Barden and Brattain received the Nobel Prize in Physics, 1956, together with William Shockley, for their researches on semiconductors and their discovery of the transistor effect.

Shockly had developed a so-called junction transistor, which has built on their slices of different types of semiconductor material pressed together. The junction transistor was easier to understand theoretically and could be manufactured more reliably.

The transistor is the three terminal, solid-state electronic device. In a three terminal device one can control electric current or voltage between two of the terminals by applying on electric current or voltage to the third terminal. This three terminal character of the transistor is what allows us to make an amplifier for electrical signals, like the one in radio.

With the three terminal transistor one can also make an electric switch, which can be controlled by another electric switch. By cascading these switches it is possible to build up very complicated logic circuits. These logic circuits can be built very compact on a silicon chip with million transistors per square centimeter. We can turn them on and off very rapidly by switching every ... seconds.

Such logic chips are at the heart of our personal computers and many other gadgets we use today.

For many years transistors were made as individual electronic components and were connected to other components (diodes, resistors, capacitors etc.) on boards to make an electronic circuit. They were much smaller than vacuum tubes and consumed much less power. Electronic circuits could be made more complex with more transistors.

It did not take long before the limits of this circuit construction technique were reached. Circuits based on individual transistors became too large and too difficult to assemble. The transistor circuits were faster than vacuum tube circuits there were noticeable problem due to time delays for electric signals to propagate a long distance in these large circuits. To make the circuits even faster, one needed to pack the transistors closer and closer together. The techniques used to manufacture

transistors led to production of very small and highly reliable electronic circuits known as integrated circuits, that is microwave integrated circuits which resulted in a hundredfold increase in the density of transistors of the chip.

Thus, electronics has extended man’s intellectual power. Microelectronics extends that power still further.

XIV. Choose the best answer:

1.The text is devoted to:

a)different types of computers;

b)contribution made by our scientists;

c)the development of transistors.

2.The aim of the text is to acquaint a reader with:

a)work and life of famous Ukrainian scientists;

b)the invention of first “point contact” transistor created by American scientists;

c)a new technology in military electronics.

3.The supporting facts to be omitted in the summary include:

a)names of famous scientists who made great contribution to electronics;

b)details of their biography;

c)experiments to reveal the nature of electrons at the interface between a metal and a semiconductor.

4.The main conclusion which can be drawn from the text is:

a)the term transistor was always used in electronics in its modern sense;

b)the invention of transistors was the spark that has ignited and will continue to ignite huge research efforts in solid-state electronics, microelectronics as the technology changes from large scale integration to very large-scale integration and very high speed integration circuits;

c)concept of “point contact” transistor was introduced very slowly into electronics.

Use the scheme proposed above and write a summary of the text “From the history of the Transistors”.

Word – Building

I. Use the following prefixes of negation to make opposites of the following words:

In-: direct, define, significant, correct, dependent; Im-: possible, measurable, mobile;

Un-: familiar, known, stable, substantial; Ir-: regular, relative, respective;

Il-: legal, limitable, logic, literacy.

II. Give nouns corresponding to the following verbs:

To convert, to relate, to calculate, to represent, to amplify, to connect, to produce, to collect, to consider, to know, to apply, to found, to direct, to inform, to determine, to add, to combine.

III. Write down the words. Underline the suffixes and state to what part of speech they belong:

Clearly, equation, emitter, depletion, classify, important, substance, useful, countless, resistor, vary, junction, depend, bipolar, deficiency, opposite, aptly, dependence, propagate, intellectual, integrate, development, hardly.

IV. Match the verbs of column A and nouns of column B to make terminological phrases:

V. Make transformations according to the model:

Model: term of atomic theory → atomic theory term.

Temperature of boiling water, the core of semiconductor diode, measurement of physical quantities, development of junction transistors, the flow of electric current, the application of varying collector voltage.

Grammar Structure

Participle and Gerund in Scientific English

I. Write the questions to which the following sentences are possible answers:

1.Joining two types (n-type and p-type) of semiconductors forms a p-n junction at their boundary.

2.Bipolar transistors remain popular for applications involving high-frequency signals.

3.Junction transistors are also known as bipolar transistors.

4.In designing the transistor the flow of the electrons from emitter to collector is very sensitive to the current into base.

5.Adding a lead resistor a much larger varying collector voltage is created.

II. State the forms and functions of Participles:

1.The substances being separated have similar chemical and physical properties.