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Integrated circuits

MicrochipsMicrochips Single electronic components are normally soldered (connected by metal) on to a circuit board by their legs. Metal tracks on the board connect the components together. Circuits that require hundreds or thousands of components would be enormous. Modern circuits use integrated circuits, or microchips, in which microscopically small components and the connections between them are built into a wafer of semiconductor material, which is normally silicon. This is why integrated circuits are often called silicon chips, or simply chips for short. The first integrated circuit was built in 1959 in the USA by Texas Instruments. Since then the number of components that can be fitted on to a chip has increased rapidly.

Different types

There are thousands of different integrated circuits. Some, such as amplifier chips or timing chips, contain a few dozen components. Others, such as computer processors or memory chips, contain hundreds of thousands, or even millions, of components.

Transistor, microchip and plastic caseTransistor, microchip and plastic case

Inside a chip

An individual transistor (1) measures just a few hundredths of a millimetre across. It consists of aluminium connections overlying layers of silicon. An integrated circuit or microchip itself (2), contains thousands of transistors and other components. It may be less than a millimetre wide. The microchip is treated with chemicals so that different parts of it act as transistors, resistors, capacitors or diodes. The delicate integrated circuit is encapsulated in a plastic case (3) to protect it. Connections are made via the legs, or connecting pins. These are plugged into sockets or soldered to a circuit board. The CPU of a PC has a single large integrated circuit, called a microprocessor (or processor).

Making a chip

The first microprocessor, the Intel 4004, went on sale in 1971. It consisted of more than 2300 transistors. A typical microprocessor today may have 730 million transistors.

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