[sdiy] Consider this DAC

[Antti Huovilainen]

On Sat, 13 Mar 2010, ASSI wrote:

> A 12bit performance level implies 72dB SNDR over the bandwidth of
> interest (you don't want to use your CV just at DC).  Getting that
> sort of accuracy without calibration is already nontrivial and keeping
> it up through temperature requires extra care.  The noisefloor is also
> awfully close in most systems and not easily lowered by much.

Please correct me if I'm wrong, but a TL072 for example has 18 nV/sqrt(Hz) 
voltage noise. For 20 kHz bandwidth (RC lowpass at 10kHz meaning settling 
time of less than 0.2 msec) the resulting RMS noise is 2.5 uV. That's 
quite a lot less than 1mV.

>> Delta-sigma is rather the other extreme of the accuracy scale.
> Not necessarily.  Audio codecs have lousy DC specs because they don't
> need any accuracy in that department, but if you need something like
> 14bit DC accuracy and an extra ten bit resolution, there's nothing to
> stop you from using a fast DAC plus modulator to get there.

True. However, the majority of cheap high resolution delta-sigma DACs are 
audio DACs, so I assumed you meant them.

Antti

"No boom today. Boom tomorrow. There's always a boom tomorrow"
   -- Lt. Cmdr. Ivanova