[sdiy] Spice beginner / Quadrature oscillator

[Neil Johnson]

Hi Karl,

> I'm trying to learn Spice (using LTSpice) and model a classic Quadrature
> Oscillator in it. the schematic i've used is widely known around the internet
> so it should work, however it's not really. 
> 
> Here's a picture of the schematic: www.sdiy.org/knas/temp/Draft1.png the
> netlist www.sdiy.org/knas/temp/Draft1.net and the LTSpice project file
> www.sdiy.org/knas/temp/Draft1.asc . 
> 
> The damned thing most of the time refuses to oscillate, the one time i've
> gotten it to it's giving me triangle outputs instead sine/cosine. The only
> thing i believe i've figured out is that it only works with specific op-amps,
> i thought for a while that it had to do with rail-to-rail capabilities but
> i've had it not work with several of those as well.

After I changed the resistors to 100k and the op-amp models to something approximating an OPA132 (this is Spice after all - everything is an approximation) I found it to oscillate nicely at around 5.4Vp-p at 1.6kHz.

Neil
--
http://www.njohnson.co.uk