I guess its a dumb question but couldnt find anything about it online. I know its possible to supply the AREF pin with 3.3 V to increase the ADC resolution.

For the project i am working on the analog voltage i will be reading will be between 0 and 2.2 and the increased resolution is a must.

I know i can use another board that has a 12 bit resolution but i really would like to make do with Uno. So i wonder if i can set an analog pin to output 2.3 V and feed it to the Aref pin.

If thats not possible please let me know why, so i can increase my knowledge

2 Answers 2


With an input voltage between 0 and 2.2 V, you can use a 2:1 voltage divider to cut the voltage in half. In your code, use analogReference(INTERNAL) to set the analog reference voltage to 1.1 V. The 1.1 V internal reference voltage is created by a bandgap circuit so is reasonably accurate.

To make the voltage divider, put two equal resistors (eg 10KΩ each) in series; connect one end of the series to your input voltage, the other end to ground, and the mid-point to an analog input pin.

  • Once you set the analog voltage to the internal bandgap voltage source, you can measure the actual voltage on the AREF pin using a multimeter. You can use that voltage to "calibrate" that arduino.
    – Gerben
    Aug 24, 2016 at 18:32
  • @Gerben That seems like easiest option, thanks for the further explanation. I also checked the oversampling, which i have never heard of before. It also seems quite valid. Again thanks for the heads up Aug 24, 2016 at 20:47

The output voltage of the "analog outputs" (which are actually PWM) are dependent on supply voltage and so are not a good choice where precision is required. Consider using either an integrated voltage reference (e.g. TL431) or a constant-current source feeding a zener diode instead.

  • Thanks for the quick reply! The things is i really try to refrain from using another circuit, allthough its relatively easy to use, the target users will have no idea how to set it up. The resolution i need is not that much, just 2.5 V /1024 instead of 5 V / 1024. sadly 3.3 V wouldnt do. Is the way i suggested still too unreliable in these conditions ? And if it is do you have any other suggestion that would not require another component ? thanks in advance! Aug 24, 2016 at 14:14
  • @Firat.Berk.Cakar You could try oversampling to get better resolution.
    – Gerben
    Aug 24, 2016 at 18:33

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