user26024: 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

user3917: 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.

26024: <p>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. </p>

<p>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. </p>

<p>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.</p>

<p>If thats not possible please let me know why, so i can increase my knowledge</p>
 3917: <p>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 <a href="https://www.arduino.cc/en/Reference/AnalogReference" rel="nofollow"><code>analogReference(INTERNAL)</code></a> 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.</p>

<p>To make the <a href="https://en.wikipedia.org/wiki/Voltage_divider" rel="nofollow">voltage divider</a>, 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.</p>
