# Scale and expand an analog signal voltage

I have an absolute pressure sensor: MPXA4115A that give me an analogical signal between 4.307 and 4.846 V. To get an altitude measurement I give it in input to an Arduino Due board which admits a maximum of 3.3 V. I am thinking to employ a voltage divider in order to scale the signal between 2.843 and 3.198 V. Now, I would like to gain resolution expanding this signal range on the entire Arduino Due's voltage range that is between 0 and 3.3 V. I am new in this matter and reading around other questions I think that what I need is a differential amplifier or an instrumentation amplifier but I am not able to do the correct choice. Before writing this question I tried to make an electrical scheme using the software LTSpice. I have imported the model of the inamp MCP6N11 but the analysis does not work and the following error message occurs:

Analysis: Time step too small; initial timepoint: trouble with node "u1:_u1:21"


More in detail I replicated the standard circuit showed in the MCP6N11 data sheet (page 27):

Here is the circuit:

I don't know if the error in the analysis is due to the fact that in the imported .txt file for the MCP6N11 is recommended to use PSPICE (other simulators may require translation).

So my question is: what kind of amplifier I have to choose?

Thank you for any suggestion.

• What is your question? Dec 4 '16 at 19:53
• Sorry! I edited my question now.. The question is what kind of amplifier I have to choose. Thanks Dec 5 '16 at 9:30
• Try adding Rser, maybe even Cpar to the supplies. Rser should be smalle enough to not have adverse effects, while large enough to not cause numerical errors due to large dynamic range. For your case, try Rser=1m (with possible CpaR=1n). There can also be the possibility that the model isn't very "cooperative" with LTspice. Dec 5 '16 at 16:47