History

The operational amplifier was originally designed to perform mathematical operations by using voltage as an analogue of another quantity. This is the basis of the analog computer, where op-amps were used to model the basic mathematical operations (addition, subtraction, integration, differentiation, and so on). However, an ideal operational amplifier is an extremely versatile circuit element, with a great many applications beyond mathematical operations. Practical op-amps, based on transistors, tubes, or other amplifying components and implemented as discrete or integrated circuits, are good approximations to ideal devices.

While op-amps were originally developed in the vacuum tube era they are now normally implemented as integrated circuits (ICs), though versions with discrete components are used when performance beyond that attainable with ICs is required.

The first integrated op-amp to become widely available, in the late 1960s, was the bipolar Fairchild µA709, created by Bob Widlar in 1965; it was rapidly superseded by the 741, which has better performance, stability, and is easier to use. µA741 is still in production, and has become ubiquitous in electronics — many manufacturers produce a version of this classic chip, recognizable by part numbers containing "741." Better designs have since been introduced, some based on the FET (late 1970s) and MOSFET (early 1980s). Many of these more modern devices can be substituted into an older 741-based circuit and work with no other changes, to give better performance.

Op-amps usually have parameters within tightly specified limits, with standardized packaging and power supply requirements. Op-amps have many uses within electronics; with only a handful of external components they can be made to perform a wide variety of analog signal processing tasks. Many standard IC op-amps cost only a few cents in moderate production volume, but integrated or discrete amplifiers with non-standard specifications may cost over $100 US in small quantities.

III Answer the following questions:

1. What is an operational amplifier?

2. Where is it used in?

3. What is an ideal operational amplifier?

IV Define the tense-forms of the verbs:

1. is controlled

2. being used

3. was designed

4. has become

5. can be substituted

6. were developed

7. can be made

V Form derivatives:

a) nouns from: difficult, to cooperate, to produce, to discuss

b) adjectives from: industry, mechanics, to continue, creation

c) verbs from: solution, production, operational, usage

d)adverbs from: comparative, necessary, direct, normal, natural, strong.

VI Translate the text in writing:

Current Conducting Materials

Conductors may be solid, liquid and, sometimes, gaseous. Metals are solid conductors. Electrolytes and molten metals are liquid conductors. Ionized air is a gaseous conductor.

Metals may be divided into two groups: high-conductance metals and high-resistance metals. The first group embraces chemically pure copper and aluminium which go to make wires, cables, machine and transformer windings. Some alloys, such as brass, bronze, aluminium alloys and steel, are also good conductors. These are preferred because of their low cost in comparison with pure metals and their high mechanical strength.

The second group of metals covers metals and alloys used in heaters, incandescent lamps, rheostats, and the like.

In addition to metals, electrical engineering makes wide use of carbon products.