Re: DDS issues...was sine generator ic solution

From: Tim Shoppa (shoppa_at_trailing-edge.com)
Date: 01/31/05 

Date: 30 Jan 2005 16:46:21 -0800

John Larkin wrote:
> Really, these things are great! But without a filter, they're junk.
>
> It is interesting that the Analog Devices datasheets used to show
> typical filters, and now they don't. And their eval boards used to
> include filters, and now don't. It's almost as if they're pretending
> that you don't need a filter.

Best case is that the device the DDS is driving has no response at
the spurs. For many real world applications of DDS's this happens to
be true.

Many of the DDS criticisms of today sound like the digital audio/CD
criticisms of the past. Heck, even the newer low-end DDS's have 14-bit
resolution, not too much different than a CD's audio format, and the
DDS is usually used at full amplitude, making its effective resolution
better than a CD player (unless you're just playing full-amplitude test
tones all day through your CD player.)

Luckily my ears lost all sensitivity above 22kHz long ago, heck I'd be
lucky
to get to 11kHz...

Tim.

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