Electronics > Beginners
Wien Bridge Oscillator Waveform Shape
Benta:
Like others wrote, you need an AGC in the circuit. Believing you can hit 3 exactly with trim pots etc. is utopia. Years ago it was pretty standard to use a fast self heating glass-bead NTC in the feedback loop. IIRC, it had part number RA53. Seems to be obsolete, though.
HoracioDos:
https://www.eevblog.com/forum/beginners/best-way-to-amplify-a-sine-wave-without-distorsion/msg1150871/#msg1150871
jose347:
some control theorem I can't remember but basically your system is either stable, oscillating or unstable which is your case, your poles are located at the rights side of the graph making the unstable response growth to infinite(in this case your supply voltage). when you use the trimpot to match the 3 gain you are actually moving the poles to the axis of the graph
*but I may be mistaken, so just ignore me
drussell:
You an also use a FET to stabilize the amplitude instead of a light bulb.
I'm trying to remember what I used the last time, probably a 2N5457 or 2N3819 or something like that, whatever I had on hand, with good results. I would have to dig up a schematic or see if I have one around on a proto board or something to double check exactly what I did... :)
drussell:
You could try something like this:
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