51 The first integrated circuit was patented by Texas Instruments. The size of an integrated circuit can range from a few square centimetres to a few square millimetres. Explain why, in your opinion, the invention of integrated circuits has changed our lives. INTEGRATED CIRCUITS A bit of history After the invention of transistors in 1947, the world of electronics developed at great speed with the creation of electronic circuits. Traditional electronic circuits consisted of a plastic printed circuit board on which electronic components (transistors, diodes, capacitors, and so on) were mounted and interconnected by conducting traces printed on it and functioning as wires. In 1958, two American engineers, Jack Kilby and Robert Noyce, independently realised that the connecting wires could be eliminated if they were integrated directly on the circuit base. So, the integrated circuit was born; the first one was patented in the USA in 1959 . How integrated circuits are made An integrated circuit (IC) assembles microscopic electronic components by building them up directly on a small piece of silicon called chip, which is provided with pins to connect it to the device where it is inserted. In this way, the circuit has all its components on one only unit, which reduces its size considerably. Advantages of integrated circuits Integrated circuits have some advantages compared to traditional ones: as all their components and connections are printed on the chip, they do not need wires; this makes them more reliable, reducing the risk of faults and enabling them to process information faster; board: tavola to patent: brevettare pin: spinotto tiny: minuscolo trace: traccia they are smaller than traditional circuits ; for this reason, they are more suitable to fit into any type of electronic devices; they can be industrially produced in large quantities; for this reason, they are cheaper. 120 ELEcTRONIcS AND ELEcTROTEcHNOLOGY Classification of integrated circuits Integrated circuits are classified according to the number of transistors they contain. This number is called Scale Integration and it gives information about the complexity of the circuit. According to the scale integration, circuits are classified in the following way: SSI (Small Scale Integration): less than 10 transistors; MSI (Medium Scale Integration): from 10 to 100 transistors; LSI (Large Scale Integration): from 100 to 10,000 transistor; VLSI (Very Large Scale Integration) from 10,000 to 100,000 transistors. The acronym ULSI (Ultra Large Scale Integration) is for circuits containing millions, or even billions of transistors, but it is not commonly used as this scale of integration is often referred to as advanced VLSI .