[sdiy] integrator / capacitor leakage

[JH.]

> The ones I have played with (AD9852, AD9835) worked down to audio 
> frequencies, and there is no reason why they shouldn't work down to the 
> minimal programmable frequency if the output circuitry is DC coupled.
> There are some that have a direct quadrature output, which would be
> handy.
> 
> > constraints. You still need a processor somewhere to load the control 
> > words into the DDS chip. Operation down to mHz involves of course 
> > another mixer... check
> 
> The really tricky part is a decent external interface anyway. I mean 
> setting a single frequency would be one thing, but I guess one would 
> also want voltage control for example.

I could live with a master clock input, which will then determine the 
frequency of the sin and cos outputs. I could just use a PLL to
step up from an ordinary VCO signal. Maybe.

JH.