6. Дайте краткие утвердительные или отрицательные ответы на следующие вопросы:

1. Is a semiconductor defined as an electric conductor? 2. Do semiconductors vary greatly in appearance? 3. May transistors replace vacuum tubes? 4. Does the state of substances depend on temperature and pressure? 5. Will you study electronics this year? 6. Have many human activities played a part in scientific inventors? 7. Did the ancients know anything about electricity?

7. Используя текст, расскажите все, что вы узнали о полупровод-

Рис. 9

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2. Прочтите текст, найдите в тексте предложения, в которых содержатся: а) основная информация; в) уточняющая информация.

THE DESTINY OF SEMICONDUCTORS

A semiconductor is often defined as an electric conductor that has a Сconductivity intermidiate between that of an insulator and that of a metal.

The more important semiconductors are: boron, germanium, silicon, selenium, phosphorus, gray tin and others.

The mechanical properties of semiconductors vary greatly. However, inиhardness, brittleness, and fracture strength, semiconducting crystals resemble insulating crystals more than they do metals. Besides their electric propertis, which in themselves may be of great variety, semiconductors vary in such physical qualities as magnetism, specific heat and thermal

3.ПрочитайтебАи выучите.

Boron – бор;

selenium – селен;

phosphorus – фосфор; Д tin – олово;

vary – меняться, разниться; brittleness – хрупкость, ломкость;

fracture – перелом, трещина;

strength – сила, прочность, сопротивление; И resemble – походить, иметь сходство;

thermal – термический.

4.Быстро просмотрите слова и выпишите те из них, которые относятся к теме “Полупроводники”.

Magnetism, diod, machinery, electricity, temperature, transistor, heat, current flow, aluminium, tin, motor, transformer, generator, subject, concept, engine, turbine, electrode, metal, brittle, wax, insulator, resistivity, direction, valence.

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5.Прочтите еще раз тексты 3 и 4 и сделайте их аннотацию на английском языке в письменной форме.

6.Задайте вопросы ко всем частям следующих предложений:

1. Semiconductors will replace vavuum tubes in many applications. 2. The more important semiconductors may be classified into three groups.

Супотреблен е страдательного залога:

7. Перевед те следующие предложения, обращая внимание на

highиvoltage. 3. The exact operation of some devices cannot be much relied upon due to their being slightly influenced by the changes in the ambient temperature. 4. If the electron is allowed to go back to the atom the balance of ghargr is restored and the atom is again uncharged or neutral. 5. The conclusions which were arrived at by the experimenter fill the demands of the present state of technical development. 6. It should be noted that each control field is given a definite polarity.7. When the microphone is being spoken into, the alternator does not producea high frequency current ofconstant amplitude.

1. When the molecules of even a good insulator are acted upon by an electric field, there is a motion of electrons due to this field. 2. the possibility of a breakdown of an insulator which is referred to in the above article is due to

8. Посмотрите видео 5 и передайте его основную идею на английском языке.

бА Д

TEXT 5

1. Составьте2 вопроса покартинке (рис.10) и обсудите ихв группе. И

Рис. 10

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2.Определите по формальным признакам, какой частью речи являются выделенные в тексте слова.

3.Найдите в ряду данных ниже слов антонимические пары.

СSolid-state, receive, continue, reverse, stop, more, positive, unobvious, send, include, long, many, evident, static, negative, short, forward, conclude, less, apparent, liquid-state, dynamic.

4Помогли. Найд те в тексте сказуемые в различных грамматических формах залогах, объясните их употребление.

5. Прочт те текст, постарайтесь понять его основное содержание и скаж те,обчто вы знаете устройствах, о которых идет речь в данном тексте. ваши знания об этих устройствах пониман ю текста?

THYRISTORS

The thyristor is a solid-state semiconductor device with four layers of alternating N and P-type material. They act as a switch, conducting when their gate receives a current pulse, and continue to conduct for as

synonymous; others define SCRs as a subset of thyristors, along with gate turn-off thyristor (GTO), triode ac switch (triac), static induction transistor

(SIT), static induction thyristor (SITH) and MOS-controlled thyristor И

(MCT). Among the latter, the International Electrotechnical Commission 60747-6 standard stands out.

Non-SCR thyristors include devices with more than four layers, such as triacs and DB-GTOs.

Function

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The thyristor is a four-layer semiconducting device, with each layer consisting of alternately N-type or P-type material, for example P-N-P-N. The main terminals, labeled anode and cathode, are across the full four layers, and the control terminal, called the gate, is attached to p-type material near to the cathode. (A variant called a SCS Silicon Controlled Switch

Сbrings all four layers out to terminals.) The operation of a thyristor can be

understood in terms of a pair of tightly coupled Bipolar Junction Transistors, arranged to cause the self-latching action.

Thyristors have three states:

conduction;и

Reverse blocking mode - Voltage is applied in the direction that would be blocked by a diode;

Forward blocking mode - Voltage is applied in the direction that would cause a diode to conduct, but the thyristor has not yet been triggered into

Forward conducting mode - The thyristor has been triggered into conduction and will remain conducting until the forward current drops below a threshold value known as the "holding current".

Function of the gate terminal

ode with no voltage applied at the gate, junctionsИJ1 and J3 are forward biased, while junction J2 is reverse biased. As J2 is reverse biased, no conduction takes place (Off state). Now if Vak is increased beyond the breakdown voltage VBO of the thyristor, avalanche breakdown of J2 takes place and the thyristor starts conducting (On state).

If a positive potential VG is applied at the gate terminal with respect to the cathode, the breakdown of the junction J2 occurs at a lower value of Vak. By selecting an appropriate value of VG, the thyristor can be switched into the on state immediately.

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It should be noted that once avalanche breakdown has occurred, the thyristor continues to conduct, irrespective of the gate voltage, until either:

(a) the potential VG is removed or (b) the current through the device (anode−cathode) is less than the holding current specified by the manufacturer. Hence VG can be a voltage pulse, such as the voltage output from a

unjunction transistor (UJT) relaxation oscillator.

These gate pulses are characterized in terms of gate trigger voltage (VGT) and gate trigger current (IGT). Gate trigger current varies inversely with gate pulse width in such a way that it is evident that there is a minimum gate charge required to trigger the thyristor.

tightly –наглухо, плотно;

Silicon Controlled Switch – кремниевый тетродный тиристор; holding current – ток удержания;

gate terminal – вывод управляющего электрода (тиристора);

7. Прочтите слова и словосочетания и назовите их эквиваленты в русском языке.

Layer; to conduct; to define; control terminal; gate; self-latching; freshold; valuejunction; avalanche breakdown; to occur; irrespecnive; hence; gate trigger voltage; gate trigger current.

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8. Найдите в тексте слова, соответствующие данным ниже определениям (дефинициям).

1) a piece of equipment, a machine or tool used for a specific task; 2) the substance of which a thing is made or composed;

3) an electromotive force or potential difference expressed in volts; С4) a brittle metalloid element that exists in two allotropic forms; occurs

principally in sand, quartz, granite, feldspar, and clay;

5) he condition of a person, thing, etc., with regard to main attributes; 6) the course or line along which a person or thing moves, points, or lies; 7) a flow of electric charge through a conductor;

и 9) the least possibleбАamount, degree, or quantity;

8) the attribute of matter by which it responds to electromagnetic forces responsible for all electrical phenomena, existing in two forms to which the signs negative and positive are arbitrarily assigned;

10) the linear extent or measurement of something from side to side, usually being the shortest dimension or (for something fixed) the shortest horizontal dimension.

9. Найдите в тексте синонимы к словам и составьте с ними предложения.

Producer, to take place, gadget, carry on, to form, case, to enlarge, acceptable, substance, to assign, to incorporate.

Д 11. Преобразуйте в предложениях страдательныйИзалог в дейст-

10. Найдите эквиваленты в русском языке для следующих выражений:

to act as…, along with…, can be understood in terms of…, arranged to cause…, to take place…, should be noted that.

вительный и, наоборот, по следующей модели:

a) A triac can be triggered by either a positive or a negative voltage being applied to its gate electrode.

Either a positive or a negative voltage being applied to triac’s gate electrode can trigger it.

b) The Thyristor block implements a macromodel of the real thyristor.

A macromodel of the real thyristor is implemented in the Thyristoe block.

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1. Low power TRIACs are used in many applications such as light dimmers, speed controls for electric fans and other electric motors.

2. However, when used with inductive loads such as electric fans, care must be taken to assure that the TRIAC will turn off correctly at the end of each half-cycle of the ac power.

С3. The GTO can be turned-on by a gate signal, and can also be turned-off by a gate signal of negative polarity.

4. The turnoff time Tq represents the carrier recovery time: it is the time interval between the instant the anode current has decreased to 0 and the instantиwhen the thyristor is capable of withstanding positive voltage Vak without turning on again.

5. You must use a stiff integrator algorithm to simulate circuits containing thyristors.

6. When theбАoutput voltage of the supply rises above the zener voltage, the thyristor conducts, shorting the power supply output to ground.

7. The stabilized high voltage DC supply for the receiver was obtained by moving the switching point of the thyristor device up and down the falling slope of the positive going half of the AC supply input.

8. The precise switching point was determined by the load on the output DC supply as well fluctuations on the input AC supply.

9. Because thyristors can be triggered on by a high rate of rise of off-state voltage, in many applications this is prevented by connecting a resistorcapacitor (RC) snubber circuit between the anode and cathode terminals in order to limit the dV/dt (i.e., rate of change of voltage versus time).

12.Прочтите текст еще раз, подготовьте 10 специальных вопросов по содержанию и предложите своим одногруппникам ответить на них.

13.Выделите в тексте элементы, которые, на ваш взгляд, являются ключевыми, и на их основе составьте сокращенный вариант текста из 10-12 предложений.

14.Прочтите текст. Предложите свой вариант заголовка. Выполните письменный перевод на русский язык.

In a conventional thyristor, once it has been switched on by the gate terminal, the device remains latched in the on-state (i.e. does not need a

continuous supply of gate current to conduct), providing the anode current has exceeded the latching current (IL). As long as the anode remains posi-ДИ

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tively biased, it cannot be switched off until the anode current falls below the holding current (IH).

A thyristor can be switched off if the external circuit causes the anode to become negatively biased. In some applications this is done by switching a second thyristor to discharge a capacitor into the cathode of the

Сfirst thyristor. This method is called forced commutation.

After a thyristor has been switched off by forced commutation, a finite time delay must have elapsed before the anode can be positively biased in the off-state. This minimum delay is called the circuit commutated turnиoff time (tQ). Attempting to positively bias the anode within this time causes the thyristor to be self-triggered by the remaining charge carriers (holes and electrons) that have not yet recombined.

For applications with frequencies higher than the domestic AC mains

15.ПосмотритебАвидео 6 и передайте их основную идею на англий-

ском языке.

16.Подготовьте сообщение на любуюДиз предложенных ниже тем.

Asymmetrical SCR

Reverse Conducting Thyristor

Light Activated SCR, or LTT – Light Triggered Thyristor

Breakover Diode

Integrated Gate Commutated Thyristor И Modified Anode Gate Turn-Off thyristor

Distributed Buffer Gate Turn-Off thyristor Base Resistance Controlled Thyristor Static Induction Thyristor

Light Activated Semiconducting Switch

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