Low Cost, 16Hz - 100kHz Sine-wave Generator circuit

Building your own signal generator is a rite of passage for any analog DIYer, but it`s one I took a long time to get around to. I already have a bench signal generator, but I decided it would be useful to have a small battery powered device that I could quickly test new effects designs with. Plus I had an enclosure from a failed project that reall
Low Cost, 16Hz - 100kHz Sine-wave Generator circuit - schematic

y needed to be put to good use. Building a sine wave oscillator is easy. Building a low distortion sine wave oscllator is less easy, and building one that can also be varied over a wide range is harder still. I could have used a ready made function generator IC like the ICL8038 or XR2206, but that seemed like cheating. Plus those parts may be difficult to find in some parts of the world, and have a clouded future, and I wanted to create something using generic parts that anyone could build. The final circuit performs remarkably well, with less than 0. 1% THD+N in the upper ranges. The logical choice for a wide range sine wave oscillator is a Wein bridge, as shown in the image on the right. This works by applying positive feedback around a gain block using a simple RC-CR band-pass filter. The circuit will oscillate at its centre frequency where the filter`s gain (and therefore the loop gain) is highest. If the two resistors and two capacitors are the same then this occurs at a frequency of: The centre frequency -and therefore the frequency of oscilation- can be varied by altering R and/or C, and this is usually accomplished by using a dual-gang pot for the resistors in the Wein network. This allows smooth control over the frequency for about one decade. Other decades are accessed by switching in different pairs of capacitors, each ten times larger/smaller than the last. However, ordinary dual gang pots are rather bulky,...

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