Attila Kinali wrote:
Moin,
On Sat, 26 Jun 2010 21:14:02 EDT
ewkeh...@aol.com wrote:
What you want is basically a Shera Board. That design has been around for
quite some time and has served me very well.
Yes. The Shera Board and similar designs serve as an example for me.
I have a total of six running
including two controlling Rubidium. There are in my opinion a couple of
problems: not every 4066 works on the design the 18 bit D/A is very hard to
find and now expensive and the single step of the D/A is intended for a 1.7
E-13 frequency step.
Yes. My goal is to update the venerable 4066 with something more
modern and have components that are easy to get trough farnell, digikey,
mouser, and all the other distributors. Yes, 16bit D/A seems to
be the maximum that is currently available. It crossed my mind
to build a 24bit R-2R D/A using discrete components, but this might
have actually a worse performance than a off the shelf 16bit D/A.
(temperature drifft, resistor values missmatch, EMI, etc)
Attila Kinali
Its possible to build a 24 bit resolution D/A using a synchronously
filtered PWM circuit.
A pair of PWM outputs and a few relatively low precision resistors and
capacitors together with a low noise low drift reference are required.
The technique takes advantage of the fact that the required EFC voltage
changes slowly and isnt updated at a highg rate.
The synchronous filter technique eliminates the very long time constant
RC filters required with an asynchronously filtered PWM waveform.
Bruce
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