A function generator is also known as a waveform generator and is an electronic device which has a very wide frequency range that can be used to produce different waveforms as its output signal. They are very versatile instruments as they can produce a wide variety of waveforms, frequencies, amplitude and duty cycle and each is suitable for different applications. Function generators called arbitrary waveform generators will allow you to generate any waveform and shape you want.
They are typically used to test analogue devices such as amplifiers and communications equipment, production testing and equipment maintenance.
There are various function generator ICs (or waveform generator ICs) available and all can be incorporated into a circuit to produce the different periodic waveforms required, common output wave types include:
- Sine or sinusoidal - consists of a single frequency, looks like a continuous wave and can be easily generated, considered the most fundamental building block of sound
- Square – non-sinusoidal waveform (has multiple sine waves of different frequencies), contains odd harmonics. Found in electronics and signal processing. Used as timing references
- Triangle – non-sinusoidal, triangular in shape. Like the square, contains odd harmonics of the fundamental frequency but the power of harmonics is twice as low as their analogues in the square wave.
- Sawtooth or saw wave – non-sinusoidal, looks like the teeth of a saw. Contains both even and odd harmonics ideal for musical sounds.
How do function generator circuits work?
A basic function generator circuit produces, for example, a triangular waveform at a frequency that can be controlled. The triangular wave is used as the base for all of the circuits other outputs, which are generated by charging and discharging a capacitor (used to store an electric charge) to shape the waveform. As the output voltage reaches an upper or lower limit, the charging or discharging is reversed by a comparator (a device used to compare two electrical signals). Different frequencies can then be achieved by varying the size of the capacitor and charge current, as well as the frequency of the base triangular wave.
Difference between a signal generator and a function generator?
A function generator produces the same waves as a signal generator but also custom shapes (advantage this device has). Some have high speed digital to analogue converters that can emulate all sorts of shapes for the signal. Sometimes there are filters to remove undesired harmonics at the output and their frequency range is usually limited at the upper levels.
