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The Wien bridge oscillator is usually denoted with a bulb to balance the gain of the system and produce stable oscillations.
Unfortunately, I don't have any bulbs, so I'm curious what a good modern replacement is, and how one would design such a replacement.
I believe you might benefit from Linear's Application Note 43f. Look for the section on Wien bridge oscillators. Jim Williams tried replacing the bulb with JFETs as well as a photocell "vactrol". Essentially, anything that has a nice linear transconductance would be a good candidate.
If anything, the app note is an excellent read and Jim Williams was a rock star :-)
A PTC thermistor is the other replacement option if you want to keep the simplicity of a two terminal passive.
Active level stabilisation is a good and useful thing, but there is sometimes much to be said for simple and crude, and often good enough is all that is needed.
Regards, Dan.
Ok, too late ... but more simpler, for information ...
