[time-nuts] DAC resistors

Neville Michie namichie at gmail.com
Tue Oct 6 23:35:31 UTC 2009


> Thanks for the suggestions,
Why I want this design is that I want to power it off my UPS which is a
solar panel floating a lead acid accumulator of 20AH capacity.
The whole show will run for years at a time.
I also want to be able to switch decades and keep full scale values  
as multiples of
1 microsecond, 10 Microsecond.............1 second.
No one seems to make dedicated BCD multiplying DACs anymore, and I  
found the
effort in making them was not so great when you wanted a micropower  
system.
With a high impedance resistor network CMOS will drive the low  
currents very accurately
with near zero voltage offsets.


I will attach a circuit, it is not quite right yet, to show the  
complete item,
I already have one running which was trimmed to death, this time I  
wanted
to get it nearly right from the beginning.

I dont think I invented this circuit, but I can not find a reference  
of how to calculate the right
decadal resistors.

cheers Neville Michie




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