# What's the difference between "operating voltage" and "input voltage"?

Hello.
I've read here (http://arduino.cc/en/Main/ArduinoBoardUno) that UNO's "operating voltage" is 5V but its "(limits) input voltage" is 6-20V. I don't understand this: why operating voltage is BELOW input voltage? I can't make the difference between "operating" and "input", because for me both have the meaning of "necessary to work".

Sorry if my question is too stupid...I am very very rookie on this.

P.D: And sorry for my english, too!!

The input is the voltage you put in to the jack socket or Vin pin to power the board. This gets regulated down on the board to the working voltage of the chip which is 5V.
You can not put a voltage higher than this 5V into the board as a signal.

OK! Understood!
THANKS! THANKS! THANKS! THANKS!

Hi,
In the Arduino Uno specifications it is given that, Input Voltage (recommended)-7-12V
Input Voltage (limit)-6-20V. What is the difference between them ? Why that range got changed?

Thank You

Hi, and welcome to the forum.
Hope this helps.

The 5volt regulator on the Uno needs at least 1volt more on it's input to make a stable 5volt.
So minimum voltage on the V-in pin is 6volt.

There is an onboard mosfet that switches off USB power when the Arduino is powered externally.
That switch point is set to 6.6volt.
So minimum voltage on V-in for USB power to disconnect is 6.6volt.

There is a reverse protection diode between the DC socket and V-in with a volt drop of ~0.7volt.
When you power the Uno on the DC socket, you have to add 0.7volt to the above statements.

Upper voltage limit could depend on the regulator's input limit (usually 20volt), or the smoothing caps (16volt on an Uno clone).
At those voltages you can't draw any current from the 5volt or 3.3volt pin (for LEDs/sensors).
With 12volt on V-in, current draw for sensors is ~100mA max.
With 6volt on V-in, that increases to ~700mA.
Leo..

Hi,
In the Arduino Uno specifications it is given that, Input Voltage (recommended)-7-12V
Input Voltage (limit)-6-20V. What is the difference between them ? Why that range got changed?

Thank You

It's all about "definitions". That's what happens when people don't define something clearly. It can lead to confusion, questions, etc.

If a circuit requires a power supply to power it up, then the word 'supply voltage' should be used. Eg, supply voltage to be applied to a particular pin. But also noting that voltage supplies come with a pair of terminals, so they need to define a supply pin for the device (that's going to be powered), as well as the other pin (eg. 0V, ground, or whatever it is).

Input voltage would usually refer to the voltage of a signal that the device is meant to process, or a control signal that is to be applied to an input pin.

On the other hand, if you look at it from another perspective, whatever voltage we are required to apply to (or inject into) a device could be considered an 'input'. This even includes power supply voltages. So, as long as everything is clearly defined in our circuit diagram or specification sheet etc, then maybe ok.

"Operating voltage" is also up to definitions. Eg. 'nominal operating voltage'..... would generally be considered as typical power supply voltage. Some devices can handle a significantly wide range of voltage....so that's why they might say 7 to 12 volt, etc.