Electronics Components: What Exactly Is an Integrated Circuit?
An integrated circuit (also called an IC or just a chip) is an entire electronic circuit consisting of multiple individual components such as transistors, diodes, resistors, capacitors, and the conductive pathways that connect all the components, all made from a single piece of silicon crystal.
To be clear, an integrated circuit isn't a really small circuit board that has components mounted on it. In an integrated circuit, the individual components are embedded directly into the silicon crystal.
Previous circuit fabrication techniques relied on mounting smaller and smaller parts on smaller and smaller circuit boards, but an integrated circuit is all one piece. Instead of just two or three p-n junctions (as in a diode or a triode), an integrated circuit has thousands of individual p-n junctions. In fact, many modern integrated circuits have millions or even billions of them, all fashioned from a single piece of silicon.
The earliest integrated circuits were simple transistor amplifier circuits with just a few transistors, resistors, and capacitors.
Now, integrated circuits are unbelievably complex. The most advanced Intel computer chip has 2.6 billion transistors.
Most of the integrated circuits you'll work with for hobby projects will be much more modest, having something on the order of a few dozen transistors. For example, the 555 timer IC has 20 transistors, 2 diodes, and 15 resistors and costs about a dollar.