integrated circuit

integrated circuit (IC), electronic circuit built on a semiconductor substrate, usually one of single-crystal silicon. The circuit, often called a chip, is packaged in a hermetically sealed case or a nonhermetic plastic capsule, with leads extending from it for input, output, and power-supply connections, and for other connections that may be necessary when the device is put to use. Integrated circuits can be classified into two groups based on the type of transistors they contain. Bipolar integrated circuits contain bipolar junction transistors as their principle elements. Metal-oxide-semiconductor (MOS) integrated contain MOS transistors as their principle elements. Some integrated circuits contain both types of transistors. Integrated circuits are also categorized according to the number of transistors or other active circuit devices they contain. An IC is said to use small-scale integration (SSI) if it contains fewer than 10 transistors. An IC that contains from 10 to 100 transistors is said to use medium-scale integration. A large-scale integration (LSI) IC contains from 100 to 1,000 transistors, and one that uses very-large-scale integration (VLSI) contains more than 1,000 transistors. All ICs now employ VLSI, and these distinctions are only of historical importance. Some integrated circuits are analog devices; an operational amplifier is an example. Other ICs, such as the microprocessors used in computers , are digital devices. Some hybrid integrated circuits contain both analog and digital circuitry; a bilateral switch, which switches analog signals by means of a digital control signal is an example of a hybrid IC. Integrated circuit functions are virtually limitless. Improvements in IC manufacturing have led to increasingly dense and capable integrated circuits. Some microprocessors, for example, contain more than one billion transistors on their chips. The smaller, denser chips can also provide speed benefits, because in high-speed devices, the length of time it takes a signal to travel a given distance can become a factor. The major fabricating steps for integrated circuits include film formation, impurity doping, photolithography, etching, and packaging. See microelectronics .

Bibliography: See M. S. Malone, The Microprocessor: A Biography (1995).

integrated circuit (IC) Complete miniature electronic circuit, incorporating semiconductor devices such as the transistor and resistor. It is used in such devices as microcomputers and pocket calculators. Monolithic integrated circuits have all the components manufactured into or on top of a single crystal of silicon (silicon chip). Hybrid integrated circuits have separate components attached to a ceramic base. Components are joined by conducting film. See also printed circuit

integrated circuit (IC) An implementation of a particular electronic-circuit function in which all the individual devices required to realize the function are fabricated on a single chip of semiconductor, usually silicon. The individual devices normally consist of semiconductor diodes, transistors, and resistors.

In MOS integrated circuits the active devices are MOSFETs, which operate at low currents and high frequencies. A very large number of MOSFETs can be packed together on one silicon chip, i.e. MOS circuits have a high packing density. They also consume very little power. The development of MOS technology has allowed extremely complex functions to be performed on a single chip.

In bipolar integrated circuits the components are bipolar transistors and other devices that are fabricated using the p-n junction properties of semiconductors. Compared with MOS circuits, bipolar circuits have higher operating speeds but have the disadvantages of high power consumption and low packing density. They are also less simple to fabricate than MOS circuits.

The improvement in the fabrication technology of integrated circuits has made possible the construction of a huge number of components on a single chip. These may be combined on the chip to make a wide variety of digital and analog circuits. The complexity of a digital circuit produced on a single chip is usually described in terms of the number of transistors involved, or sometimes of the number of logic gates. This leads to the following differentiation:

VLSI	very large-scale integration;
LSI	large-scale integration;
MSI	medium-scale integration;
SSI	small-scale integration.

Digital integrated circuits are often represented by their logic function rather than their electronic function in order to ease their understanding. See also hybrid integrated circuit.