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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.

wein bridge oscillator for wikipedia

Mike Spivey
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Andrew Spott
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  • Read Andy's comment about JFETs here: http://electronics.stackexchange.com/questions/78388/what-is-the-function-of-the-bulb-in-a-wien-bridge-oscillator -- which is also a link to the right of your question. – jonk Sep 09 '16 at 20:19
  • Also, some discussion about using a JFET part way down this page: http://www.learnabout-electronics.org/Oscillators/osc34.php -- just from a quick google search for you. – jonk Sep 09 '16 at 20:21
  • I was kind of hoping for an expansion of that idea. – Andrew Spott Sep 09 '16 at 20:21
  • Can you expand your question to include the jfet topology and by then talking about the aspects of the jfet circuit where you need more thought added? Or are you fishing for a still different answer? – jonk Sep 09 '16 at 20:24
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    Jfets aren't the only option for agc, so I would rather not limit answers to just jfet agc circuits. I'm going to let this question fester for a bit (I don't have time to rewrite it right now), but maybe I'll refocus it later. – Andrew Spott Sep 09 '16 at 20:27

3 Answers3

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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 :-)

Mario
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Daniel V
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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.

Dan Mills
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0

Ok, too late ... but more simpler, for information ...

enter image description here

Antonio51
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