INTEGRATED CIRCUITS

INTEGRATED CIRCUITS:

 An integrated circuit, or IC, is small chip that can function as an amplifier, oscillator, timer,microprocessor, or even computer memory. An IC is a small wafer, usually made of silicon, that can hold anywhere from hundreds to millions of transistors, resistors, and capacitors. These extremely small electronics can perform calculations and store data using either digital or analog technology.

Digital ICs use logic gates, which work only with values of ones and zeros. A low signal sent to to a component on a digital IC will result in a value of 0, while a high signal creates a value of 1. Digital ICs are the kind you will usually find in computers, networking equipment, and most consumer electronics.

Analog, or linear ICs work with continuous values. This means a component on a linear IC can take a value of any kind and output another value. The term "linear" is used since the output value is a linear function of the input. For example, a component on a linear IC may multiple an incoming value by a factor of 2.5 and output the result. Linear ICs are typically used in audio and radio frequency amplification.

Have you ever heard of a 1940s computer called the ENIAC? It was about the same length and weight as three to four double-decker buses and contained 18,000 buzzing electronic switches known as vacuum tubes. Despite its gargantuan size, it was thousands of times less powerful than a modern laptop—a machine about 100 times smaller.

If the history of computing sounds like a magic trick—squeezing more and more power into less and less space—it is! What made it possible was the invention of theintegrated circuit (IC) in 1958. It's a neat way of cramming hundreds, thousands, millions, or even billions of electronic components onto tiny chips of silicon no bigger than a fingernail. 

What is an integrated circuit?

Open up a television or a radio and you'll see it's built around a printed circuit board (PCB): a bit like an electric street-map with small electronic components (such as resistors and capacitors) in place of the buildings and printedcopper connections linking them together like miniature metal streets. Circuit boards are fine in small appliances like this, but if you try to use the same technique to build a complex electronic machine, such as a computer, you quickly hit a snag. Even the simplest computer needs eight electronic switches to store a single byte (character) of information. So if you want to build a computer with just enough memory to store this paragraph, you're looking at about 750 characters times 8 or about 6000 switches—for a single paragraph! If you plump for switches like they had in the ENIAC—vacuum tubes about the size of an adult thumb—you soon end up with a whopping great big, power-hungry machine that needs its own mini electricity plant to keep it running.

Photo: An integrated circuit from the inside. If you could lift the cover off a typical microchip like the one in the top photo (and you can't very easily—believe me, I've tried!), this is what you'd find inside. The integrated circuit is the tiny square in the center. Connections run out from it to the terminals (metal pins or legs) around the edge. When you hook up something to one of these terminals, you're actually connecting into the circuit itself. You can just about see the pattern of electronic components on the surface of the chip itself. Photo by courtesy of NASA Glenn Research Center (NASA-GRC).