6. Make up sentences with these expressions.

be related to as well

consist of such as

be made from compensate for

UNIT 2

Read and translate the text, reproduce it orally.

At the modern stage of scientific and technological development, microelectronics is rapidly gaining ground and its advances today largely determine progress in many branches of industry. The need for lighter, more compact. and more reliable radioelectronic equipment capable of performing the functions of growing complexity has led to research into ways and means of achieving the aims. Since discrete transistors could not meet the above requirements, search for principally new approaches to microminiaturization, low-cost, and reliable electronic systems has brought the concept of producing circuits in one tiny die, or chip. Microcircuit techniques gradually become available, which resulted in the replacement of discrete elements by solid state and hybrid microcircuits, or integrated circuits (ICs) for short.

Microelectronics is the next stage of development of electronics, which uses a variety of physical, chemical, circuit techniques and fabrication methods for the research, development, and utilization of ICs and miniature electronic devices.

Vacuum tubes were the first generation of the element base of radioelectronic equipment, and discrete semiconductor devices were the second; integrated circuits and large-scale integrated (LSI) circuits represent the third and the fourth generation of that base respectively. The trend today is to lay the foundations of functional microelectronics.

As regards their technologies, ICs fall into two categories, monolithic ( solid-state ) and hybrid. The basic advantage of monolithic technology is that it offers the possibility of producting high-quality active elements.

Monolithic circuit production requires an extremely large initial outlay to set up economically warranted facilities. Considering that monolithic circuit fabrication is a complex and labor consuming process and, besides, it involves large investments in tooling and requires a lengthy period to design and produce a prototype circuit, monolithic technology is economically justifiable only in long production runs, i. e. where large quantities of ICs are produced in single and repeated manufacturing cycles.

Hybrid circuits (hybrids) contain thin-film or thick-film passive elements and semiconductor active discrete elements, or IC components. Thin-film hybrid technology is preferable where there is a need to produce special microcircuits (microassemblies) in comparatively low quantities.

An advantage of thin-film technology is its flexibility which enables the engineer to select materials with optimum parameters and characteristics and in essence achieve any configuration of passive elements.

Exercises

1. Give synonyms to:

modern, rapidly, determine, principally, device, foundation, quantity, contain, select.

2. Give antonyms to:

reliable, complexity, new, tiny, short, advantage, active, low, thin, next, possible.

3. Match the words with their definitions:

determine do a piece of work.

perform decide, find out precisely.

tiny combine into a whole.

integrate make use of.

utilize very small.

flexible sth needed or demanded.

requirement easily bent without breaking.

5. Form abstract nouns from the adjectives given below.

dangerous, helpful, useless, respective, beautiful, logical, comparable, careless.

6. Make up sentences with these expressions:

as regards in essence achieve the aim

for short for the research of to lay the foundation

gain considering that ground

UNIT 3

Read and translate the text, reproduce it orally.

Integrated resistors can be made in a variety of ways. The elements that can serve as resistors are individual portions in the bulk of a semiconductor (bulk resistors), pn junctions biased in the forward or reverse direction, and transistor structures.

Integrated circuits most often use resistors in the form of thin semiconductor layers diffused into the crystal surface and isolated from each other. The resistors of this type are known as diffused resistors, which show linear characteristics and obey well Ohm’s law in the working range of voltages. The impurity concentration gradient present in diffused layers results in a higher conductance of strongly doped silicon layers near the surface.

Diffused resistors are generally grown at one of the stages of manufacture of a transistor in a single technological cycle. Resistors with a low value of receptivity p are made during the diffusion of an emitter region, and those with a medium value of p at the stage of diffusion of a base region. Besides, resistors of high nominal values can be grown in the collector region or in the substrate.

Diffused resistors should have the smallest possible dimensions for which reason it is expedient to form them from high-ohmic layers of small cross section in the shape of narrow meandered strips. The strips terminate in contact pads, with ohmic contacts produced in strongly doped n+ regions. Bends and branches affect the value of an integrated resistor.

Diffused resistors have a relatively high value of TCR (temperature coefficient of resistance a) because the electron and hole mobilities are temperature dependent. The carrier mobility commonly decreases with growing temperature. The variation of hole mobility with temperature becomes less noticeable as the impurity concentration grows. So, diffused resistors formed on the p layer have a positive temperature coefficient (TC) that depends on the impurity concentration, and those produced on the n layer have a negative TC.

Diffused resistors display a nonlinear resistance variation because the pn junction widens with increasing voltage, so the layer cross section decreases and the nominal value grows.

The maximum operating voltage of a resistor depends on the pn junction reverse breakdown voltage which varies only with impurity concentration.

The power dissipation of a resistor is largely a function of its maximum operating temperature. The factors that determine this upper temperature limit are the required stability of the resistor value, range of variations in TCR, and the maximum operating temperatures of other resistors. In microcircuits, resistors heat up most heavily. Overheating is given due consideration in calculating the optimum area of a resistor: too small an area causes an increased heating of the resistor and may lead to breakdown.

Exercises