http://www.analog.com/en/rfif-c...index.html

AD9833 - 10 USD at Digikey. It's this expensive?

http://www.elecfree.com/circuit/O...y-ic-1458/

It's not a single IC, but it's a starting point, if you want to "roll-yer-own."

IIRC, the 8038 has a large switching transient at dv/dt=0, and I doubt this circuit will be very different in that respect.

There's also XR2206 and XR2207, but I suspect they're no more available than XR8038.

RE

We have precision, very low distortion oscillators for exactly that application Ap, I can send you some circuit diagrams. We measure the CURRENT in the LVDT, which is a more accurate method of stabilising the reference levels than a voltage.

Our favourite method uses a Colpitts oscillator as the signal source. That needs a tiny transformer, but you can use any oscillator topology you like, provided you can readily control its amplitude.

If you use a DDS chip, you still need to get precision amplitude, so you could feed a dds with a reference, and use the same reference for the A/D circuits after the demodulation.

Steve