[time-nuts] yet another GPSDO design, or so

jimlux jimlux at earthlink.net
Tue Jun 29 13:03:56 UTC 2010

Bruce Griffiths wrote:
> Attila Kinali wrote:
>> Moin,
>> On Sat, 26 Jun 2010 21:14:02 EDT
>> EWKehren at 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.

or with a pair of current output DACs and a resistive divider/summer so 
you have a "high order" and "low order" voltage.

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