Basic Audio is a free introductory textbook to the basics of audio physics and electronics. See the editorial for more information....

Oscillator Waveforms

Author: N.H. Crowhurst

Producing square waves

Audio requires waveforms other than sine waves. Square waves used in transient tests can be produced simply by amplifying sine waves in a circuit using diodes that start to conduct when the voltage reaches a specified point. This kind of circuit chops off the top and bottom of the sine wave, making something very much like a square waveform. If 9/10 of the sine wave is chopped off, the slope of the line joining the horizontal sections is very nearly vertical. The sides can be made even steeper by amplifying this wave again, and again chopping off 9/10 of it.

Sawtooth waves are made by a variety of means. A simple one is a circuit in which a steady current flows into a capacitor until the voltage across it reaches a specified point. This starts a quick feedback action through a couple of tubes that rapidly discharges the capacitor to its original level, from which it starts the charging sequence all over again. The sawtooth waveform is used for the sweep voltage in oscilloscopes and in electronic musical instruments as a basis for the variety of musical tones. A sawtooth wave has a very useful combination of fundamental with all of its harmonics, whereas the square wave possesses only the odd harmonics.

Producing a sawtooth wave

Last Update: 2010-11-03