- •Remember!
- •Word-substitutes
- •Correct the sentences where necessary. Some of these sentences need a/an.
- •Complete the sentences using the following. Use the where necessary.
- •Fill in the gaps with articles a/an, the where necessary.
- •Translate the sentences from Russian into English. Mind the usage of articles.
- •Use set expressions given in the grammatical table above to complete the following sentences.
- •Find sentences where that (those) are in the function of word-substitutes.
- •Translate the following sentences in writing paying attention to the translation of the word that.
- •Read the text. Is it obligatory to translate the word ones? Design by Computer
- •Translate the sentences into Russian paying attention to the meaning of the word one.
- •Translate the sentences. Mind the words that, one, those.
- •Specialist Reading
- •Intrinsic Silicon
- •Read the text about intrinsic silicon. Mark the following sentences as true (t) or false (f).
- •New, Unusual Semiconductor is a Switch-Hitter
- •Work in groups. Group 1 summarize everything that you know about
- •Give interesting facts that you know in the sphere of physics, electronics, mathematics etc. Your group mate will act as an interpreter from Russian into English.
- •Text b Communicating Through the Earth part II
- •In Russian write a content-based summary of the text you have translated.
- •Make a summary translation of the text you haven’t read.
- •Make an oral summary in English of the whole text.
Read the text. Is it obligatory to translate the word ones? Design by Computer
Belarus will now design multistorey buildings with the help of computer.
An electronic computer system developed at building and assembling enterprises will help reduce designing time by 1/4 (one-fourth). Designers have at their disposal 4,000 various structural components from which the computer chooses the most suitable ones.
Translate the sentences into Russian paying attention to the meaning of the word one.
The theory of the basic devices in radio engineering — radio transmitting and radio receiving ones — was developed by Soviet scientists.
To understand what laser is one has to understand how light is generated.
The input unit to be described here is a new one.
One can make matter vibrate in different ways.
In future power stations will use the principle of direct conversion of solar energy into electric one.
Due to radioactive elements one can measure the thickness of various materials.
He knew that no one could help him.
The history of the exploration of the Urals has been a long one.
I know only one solution of this problem.
Translate the sentences. Mind the words that, one, those.
Since the grid is nearer to the cathode, its effect on the electrons is much greater than that of the plate.
The element that attracts electrons from the cathode is called the plate.
When capacitors are connected in series, the total capacitance is less than that of the smaller capacitor.
The symbol for the PNP transistor is almost identical to that of the NPN transistor.
The flow of electrons along a wire can be compared to that of liquid through pipes.
The basic amplifier action of tetrodes and pentodes is the same as that of triodes.
A semiconductor is a material having a conductivity between that of a metal and an insulator.
A grid placed near the space charge is better able to stop the electrons than the one placed farther away.
The best value of load resistance is normally one that will give a reasonable amount of gain.
The middle-frequency range is one in which coupling capacitor can be neglected.
The intrinsic semiconductor is the one in which some holes and electron pairs are created by thermal energy, even though there are no impurities in it.
A class-B amplifier is one in which the grid is biased at or very near cutoff.
For many applications the characteristics of the junction diode are better than those of the vacuum diode.
Extrinsic properties are those of a semiconductor modified by impurities within the crystal.
Specialist Reading
Intrinsic Silicon
The word semiconductor, which features so prominently in present-day electronics, means rather generally a material which has electrical conductivity half-way between that of a metallic conductor, and that of an insulator. However, there are some specific properties that distinguish semiconductors used for electronic devices from materials which generally might be said to have semiconducting characteristics (for example, a wet insulator may very well be a semiconductor in .some general sense, but it is regarded as hazardous rather than as useful electrically).
Silicon is the most widely used of semiconductors. In the Earth's crust, it is the second most plentiful element, next to oxygen, but it appears only in oxide compounds known as silicates. Quartz is one form of silicon oxide, and sand, that very common stuff, is mostly composed of fine particles of silicon oxide. To be useful for electronic device manufacture, the silicon must be obtained in its elemental form, that is, free of oxygen, and also in its single crystal form.
Single crystal means that the atomic lattice structure making up the silicon is regular throughout; in effect, the lattice as "seen" from any lattice point within the silicon appears the same in all directions. Other impurities, especially boron which associates easily with silicon, must be removed or reduced to negligible level. A high-purity silicon is specified as semiconductor grade silicon. In later stages of processing, certain chemical elements, or impurities, are purposely added again in precisely controlled amounts to alter the electrical conductivity.
The manner in which the conductivity is altered is all-important in determining the characteristics of devices fabricated in the silicon, but before we consider this we shall compare the resistivity of intrinsic silicon with that of a good electrical conductor, copper, and that of a good electrical insulator, ceramic. Within an order of magnitude, the volume resistivities are:
Copper |
10-4 ohm-meters |
Intrinsic Silicon |
103 ohm-meters |
Ceramic |
1010 ohm-meters |
In the three cases just considered, conduction, to the extent that it does occur 2 is a result of the movement of electrons under the influence of an applied electric field. In copper, there is an abundance of what are termed conduction-band electrons, which are only very loosely bound to parent atoms. They move relatively freely under the influence of any externally applied electric field, and account for the high conductivity of copper. In ceramic, almost all electrons are very tightly bound to parent atoms. The density of conduction-band electrons is negligible, with the result that conductivity is also negligible. Of course, the function of an insulator is to prevent conduction, and most practical problems with insulators result from unwanted conduction through surface contaminants.
With intrinsic silicon, two distinct condition mechanisms must be taken into account. Conduction-band electrons are present which contribute to conduction, although the density is many orders of magnitude less than that in copper. These conduction-band electrons originate by being shaken loose from parent atoms, by the thermal energy which is present naturally because the semiconductor is at a finite (e.g. room) temperature.
The electron energy band from which they are shaken loose is termed the valence band. Vacancies, or holes, will be left in the valence band by those electrons which leave and these holes allow the valence-band electrons to contribute to the conduction also by a “hopping” process under the influence of an applied electric field. Rather than describe the process as one of electrons hopping from atom to atom wherever holes permit this, it is vastly more convenient to describe it in terms of the movement of holes. In this way, the concept of hole conduction arises.
The two distinct conduction mechanisms in intrinsic silicon are known, therefore, as electron conduction and hole conduction.