LTSPice model of low distortion sine wave generator - Help needed

[RichardM]

Hi

I thought I would try and build the 1khz sine wave circuit published by Elektor in LTSPice

https://www.elektormagazine.com/articles/reference-sine-wave-generator

and discussed here

https://www.eevblog.com/forum/testgear/question-cheap-pure-sine-wave-genertor-1khz/50/

Unfortunately I cannot seem to get any sensible output, certainly no sine wave. The circuit has a bulb (12V, 50ma) so perhaps thats what I am modelling incorrectly ? Theer is a bulb sub circuit floating around on the web I used.

Any hep appreciated

Richard

[Kleinstein]

The light bulb part is not easy to simulate. The regulation with the light bulb as PTC is based on a thermal effect of self heating that is no includes in most models.   For the practical implementation the type and size of the light bulb can make a difference.

[RichardM]

Ok, thanks. I guess simulation is off the table and the breadboard is the way forward.

[Kleinstein]

One can still do a simulation for much of the circuit. One may just have to change the amplitude regulation, or find a PTC model that includes self heating.

[RoGeorge]

The exact model to simulate the incandescent light bulb is not so important, because in the given schematic the light bulb is used as a voltage controlled resistor with a big integration constant (~seconds).

My guess is the exact I-V shape for the filament doesn't matter much, but just in case you are curious how it looks like, I measured two light bulbs some time ago:



https://www.eevblog.com/forum/projects/resistance-of-incandescent-light-bulbs/msg3720658/#msg3720658

No matter how good your light bulb model is, the distortion level differences between the simulated and the real circuit might vary widely in practice.