An Integrated Circuits consists of inseparably associated elements on a single substrate and is made up of semiconductor material. Impurities are diffused into a single crystal-silicon to form an integrated circuit. This crystal-silicon now serves as a semiconductor material.
Merely etching the silicon by means of electron beams can also make silicon a semiconductor. Hundreds of identical IC s are made at a time on a single wafer. This wafer is several centimeters wide, which is then subsequently, sliced into individual IC s called chips. Chips are assembled into packages that contain external electrical leads. These facilitate insertion of other circuits or components into printed circuit boards.
Use of Integrated Circuits
ICs have made the development of many new products possible in consumer electronics, including personal calculators and computers, digital watches, and video games. They are also being used to lower the cost of existing products, such as appliances, televisions, radios, and high-fidelity equipment and to improve their performance. Tiny circuit (or an IC) can perform analog functions like amplification and can be combined with different components to work as a complex system.
Integrated Circuits are used in a variety of devices, including microprocessors, audio and video equipment, and automobiles. Computer technology, in particular, has benefited greatly. The logic and arithmetic functions of a small computer (ALU unit) can now be performed on a single VLSI (Very Large Scale Integration) chip called a microprocessor.
And the complete logic, arithmetic, and memory functions of a small computer (all functions controlled by Control Unit) can be packaged on a single printed circuit board or chip.
The microprocessors are among the most advanced integrated circuits, which control everything from computers to cellular phones to digital microwave ovens.
Integrated Circuits have become ubiquitous only a half-century after their development. Computers, cellular phones, and other digital appliances are now inextricable parts of the modern societies, i.e., modern computing, communications, manufacturing and transport systems, including the Internet, all depend on the existence of integrated circuits.
Advantages of IC s over Discrete Circuits
ICs have consistently migrated to smaller sizes over years, allowing more circuitry to be packed on each chip. As the size shrinks, everything else improve, e.g., the cost per unit of IC is reduced, the switching power consumption goes down, and the speed increases.
A Discrete Circuit is a circuit whose components like transistors, resistors, etc., are soldered or otherwise connected mechanically. However, an Integrated Circuit is a circuit that has its own transistors, resistors and diodes. There are two main advantages of ICs over discrete circuits - cost and performance.
Cost is low because the chips, with all their components, are printed as a unit by photolithography and not constructed a transistor at a time. The cost of designing and developing a complex integrated circuit is quite high. However when spread across typically millions of production units the individual IC cost is minimized.
Performance is high since the components switch quickly and consume little power, because the components are small and close together. The small size of IC s allow short traces, which in turn allows low power logic (such as CMOS) to be used at fast switching speeds.
The integration of large number of tiny transistors into a small chip was an enormous improvement over the manual assembly of a circuit of various discrete electronic components.
Development of Integrated Circuits
It seems that it was destined to invent the integrated circuit. Two individual inventors, unaware of each other's activities, invented almost identical structure (the integrated circuits) at nearly the same time. Jack Kilby of Texas Instruments and Robert Noyce of Fairchild Semiconductor were the people who developed the Integrated Circuits in 1950s.
As with many inventions, two people had the idea for an integrated circuit at almost the same time. Transistors were used in almost everything from radios to phones to computers. But the manufacturers wanted something that is even better. Sure, transistors were smaller than vacuum tubes, but for some of the newest electronics, they weren't small enough. So, the scientists wanted to make a complete circuit -- the transistors, the wires, everything else they needed -- in a single blow.
One day in late July, it suddenly occurred to Jack Kilby that all parts of a circuit (not just the transistor) could be made out of a semiconductor material, and what better than silicon Kilby built a working model of an IC by September 12, and on February 6 the next year, Texas Instruments filed a patent. Their first "Solid Circuit" was the size of a pencil point.
However in California, Robert Noyce who worked at Fairchild Semiconductor realized a whole circuit could be made on a single chip. Noyce called this a "unitary circuit and also applied for a patent on the idea.
Today, both men are acknowledged as having Integrated Circuits independently conceived of the idea. Jack Kilby holds patents on over sixty inventions. He is also well known as the inventor of the portable calculator (1967). In 1970 he was awarded the National Medal of Science. Robert Noyce, (with sixteen patents to his name), founded Intel. As we all know, the company is responsible for the invention of the microprocessor, in 1968. But for both, the invention of the integrated circuit stands is one of the most important innovations of mankind.
Classification
A CMOS 4000 IC Integrated Circuit is classified into analog, digital and mixed signal (both analog and digital on the same chip). Digital integrated circuits may contain one to millions of logic gates,
flip-flops, multiplexers, and other circuits in a few square millimeters. The small size of these circuits gives high speed, low power dissipation, and reduced manufacturing cost compared with board-level integration. Latest server processor from Intel had 4 billion transistors on a chip. Analog Integrated Circuits can perform the functions like amplification, active filtering, demodulation, mixing, etc. ADCs and DACs are the key elements of mixed signal ICs. They convert signals between analog and digital formats.
Digital Integrated Circuits:
Many scholars believe that the digital revolution brought about by integrated circuits was one of the most significant occurrences in the history of mankind. Digital memory chips belong to the family of integrated circuit and are crucially important to the modern information society. The classification of Digital Integrated circuits is based on number of transistors and other electronic components they contain:
SSI (small-scale integration): Up to 100 electronic components per chip
MSI (medium-scale integration): From 100 to 3,000 electronic components per chip
LSI (large-scale integration): From 3,000 to 100,000 electronic components per chip
VLSI (very large-scale integration): From 100,000 to 1,000,000 electronic components per chip
ULSI (ultra large-scale integration): More than 1 million electronic components per chip
Digital ICs are fabricated in a layer process, which includes these key process steps:
Imaging
Deposition
Etching
Doping, cleaning and planarisation steps supplement the above steps. The digital (or logic) Integrated Circuits are mostly used in microprocessors and memories.
An Integrated Circuit - DSP (Digital Signal Processor) - is designed for high-speed data manipulations, image manipulations, communications, and data-acquisition and data-control applications. Dynamic RAM is nothing but a Digital Integrated Circuit that contains capacitors.
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