wave generator circuit
One way to generate a sine wave is to pass a square wave through a low-pass filter ..
The high-order harmonics will be filtered out, leaving only the fundamental; the higher the order of the filter, the purer the sine wave produced ..
And three square waves shifted by 120° can be easily generated using simple, small-foot-print microcontroller such as, for example, PICAXE-08 (8-pin) ..
I know this is not ANALOG solution, but you may consider also this option ..
Regards,
IanP