Dear Rik, Gary, LF Group,

If that is the case there is no need to get a nice sine (through a LPF and bufferamplifier), most convenient is to pick up the 274kHz signal somewhere at TLL or CMOS level.

73, Rik  ON7YD

The output of the DDS is actually the output of a digital to analogue
converter, and at 274 kHz the signal on the output pin of the DDS chip
will be a pretty good approximation to a sine wave anyway. The function
of filtering in the circuit is to remove "alias" frequency components
arising due to the sampled-data nature of the output signal. So there
isn't actually a logic-level signal in the circuit. You could of course
add a squaring circuit giving a logic-level square wave after the DDS
output filter.

Cheers, Jim Moritz
73 de M0BMU