The World’s Simplest Circuit: Six Oscillators on a Chip, Guaranteed to Work
Nicolas Collins · 2009
In the contrarian spirit of hacking, the first circuit we build from scratch is based on the misuse of an integrated circuit (IC) never intended for making sound. The “Hex Schmitt Trigger” is a CMOS digital logic chip consisting of six identical “inverters.” An inverter takes a logical input, 1 or 0, and puts out its opposite (so 1 becomes 0, 0 becomes 1)— it is one of the fundamental Boolean building blocks that goes into the design of the computers we’ve come to depend on for so much of our work and play. This particular implementation of an inverter is useful to us because it runs for a long time on a 9-volt battery, it is very cheap, and it contains a circuit element known as a “Schmitt Trigger” whose fine points you don’t need to understand at this point but, trust me, transforms the chip from a simple digital no-man (as opposed to a yes-man) into a versatile sound generator.