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How to get Accurate 0 to 10V ?

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nick703

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Hello first of all i have use PIC32MX575F256H and mcp4922 DAC using SPI. And i am able to get 0 to 3.3V using mcp4922.

Now my question is how to convert this dac 0 to 3.3V <--> 0 to 10V?
1st come to mind is using non-inverting amplifier with gain setting.

gain = 10/3.3 = 3.03 (Is that correct?)

and choose the value of r1 and r2 like 1k and 330ohm.

is that accurate method to achieve 0 to 10v output using 12-bit resolution?

and if any other then please give me some advise.
 

The ratio 3.03 is correct, but you implement the formula in a wrong way, because there is a "+1" inside it. You will confirm this with a quick web search. Use 1% resistors at worst, and have a proper grounding because even a few mV voltage drop will reduce the accuracy. Of course you must select a proper opamp, for example you need low offset. My opinion is that it is very difficult not to loose anything of your accuracy. You must design this very good.
 
Hi,

Don't make it too difficult.
Just use an amplifier that outputs a bit more range than you need:
Maybe: -0.1V ... 10.1V
Then do the calibration with software.
A simple ADD and MULTIPLY solves the accuracy problems.

Klaus
 

Your "0 to 3.3V" is probably a fundamental limit to
accuracy - probably a 5% supply, and full of noise
if it's commoned with the uC?

I might suggest picking a DAC which has an output
independent of its power supply (one that takes a
full-scale precision reference input, maybe). A REF10
precision reference, and one of many voltage mode
DACs, or a current mode DAC, a precision resistor
multi-element SIP and a precision op amp for the
current-to-voltage conversion (and the feeding of
the +10.000V reference voltage to the DAC IREF
port; some DACs have the precision resistors on
chip for the current feed and op amp use so the
precision external ones aren't needed).

Now, this sort of setup will require you to provide
+/-15V supplies (presuming you want a good clean
0.000V at one end, you need something that can go
below it with adequate drive - no single supply op
amp).

Accurate, you indicate to be 12 bits or 0.024%-ish
(2.4mV LSB). A 5% tolerance supply fed straight
through a VDAC isn't going to come close.

But then, just because you -have- 12 bits does
not mean you -need- 12-bit accuracy. How hard
you have to try, and how many mistakes you have
to learn from, depends a lot on having sane goals.
Might take a step back and put numbers to the
accuracy requirement, before getting fired up about
any particular approach.
 
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