Quadrature VCO

[Chris MacDonald]

Is it possible to build a QVCO around a single LM13700?  I have tried to
make one by starting with a 2nd order state variable filter but was
unable to achieve strong, stable oscillation without clipping on at
least one of the waveforms.  Did I miss something here?  Is there an
otherwise "standard" or "classic" circuit for a QVCO?  I don't need
through-zero or anything, just nice sine waves up to 25kHz or so.

Thanks,

Chris MacDonald