I'm making a function generator which works in the audio range for a college project. I'm not allowed to use microcontrollers or any digital chips. So I'm using a Wien Bridge oscillator with a pot to generate variable sine wave. It is followed by a Schmitt trigger to generate square waves and finally an integrator to get triangle wave. I found this schematic on the web for the Wein bridge:
Could you replace the two variable 100k pots by a single pot? If not, is it possible to somehow mechanically (or electrically) gang the two different 100k pots? I'm trying to avoid using a single double-ganged-potentiometer to save cost.
I would like my final design to have only two pots. One for frequency and one for amplitude.
Best Answer
Are you forced to use the WIEN oscillator (named after Max WIEN) topology ? There are other oscillator types with single-element control - however with two operational amplifiers.
Here is a corresponding link: http://m.eet.com/media/1143038/17995-82202di.pdf
I like to mention that for frequency tuning you only have to tune one single grounded resistor. More than that, the quality of the output signal (THD) - for most applications - will be sufficient, even without additional amplitude control mechanism.
EDIT: To all who also are interested in the update of the referenced paper: Try this link (I hope it works) and search for "A novel harmonic Oscillator: GIC Resonator" : https://www.researchgate.net/profile/Lutz_Von_Wangenheim/publications