Match the words with their definitions. predominant use up completely
predominant use up completely.
exhaust lay or place on.
impose having more power or influence than others.
redundancy moving from one place to another.
discern unneeded or surplus.
migration see clearly.
abandon go away not intending to return.
Form as many related words as you can.
examine, educate, minor, develop, definite, operate, process, compare, divide, compute, suspect, consider, reflect, represent, change, combine.
Make up sentences with these expressions.
would rather not until
only after had better
even if but for
what if used to
UNIT 8
Read and translate the text, reproduce it orally.
Reliability is the probability that a circuit will perform its intended function for a specified interval of time under stated conditions. This quantity is thus a function of time and conditions of operation. A common approach to evaluate the reliability of circuits is to test a batch of fabricated devices for service life and performance under specified operating conditions. If failures have occurred in the batch of devices after a definite length of time, we can determine the failure probability per unit time, which is known as the mean failure density, or failure rate.
In the initial period of testing, failures occur rather often because the batch contains a certain number of unreliable pieces due to material contamination, errors in assembling, and other causes. As poor circuits gradually fail to operate, the failure rate for the remaining circuits decreases and finally reaches a constant value. In this second period of constant failure rate, failures result from random, uncontrollable causes. In the third period of testing, the failure rate again rises because of inevitable wear and aging.
It is thus obvious that for a system to be reliable, it must contain the circuits that have passed the trial run. The use of ICs has appreciably raised the reliability of equipment due to a sharp decrease in the number of passive components and various connections. However, the reliability of very complex ICs is in principle lower than that of simple components. A large body of the now available statistical information can be used to compare the reliability of various types of ICs designed to operate in most diverse conditions. The failure rate of modern ICs varied from 10-6 to 10-9 and approaches the value typical of highly reliable discrete elements. As a matter of fact, it is impossible to adjust the load on each IC element separately. A decrease in the supply voltage may have no strong effect on the life of, say, a capacitor, but will disturb the operation of the circuit as a whole. The power consumption of digital circuits also depends on the fan-in and fan-out.
The failure rate of MOS (Metal-oxide semiconductor) and bipolar ICs of the identical complexity is approximately the same, provided the test, environmental, and operating conditions, along with the quality control requirements, are similar.
In comparison with monolithic circuits, hybrids fail faster. The failure rate varies with the particular design and the technology employed. The thing is that some operations in the hybrid manufacturing cycle are not yet amenable to automation and must be done manually.
Multichip circuits are less reliable than monolithic circuits because of a large number of chip-to-chip connections whose damage can be responsible for failure of the entire circuit. In an effort to improve the reliability of these circuits, development engineers strive to raise the complexity of a circuit on the single chip, reduce the number of chips, and use thin-film connections.
Exercises
1. Give synonyms to:
entire, damage, approximately, quantity, error, remain, constant, obvious, diverse, contamination, batch.
2. Give antonyms to:
failure, reduce, impossible, sharp, modern, after, manual, these, controllable, connection, diverse.