Voltage Divider Tutorial For Learners

A voltage divider is a circuit that creates a smaller voltage from an enter voltage by utilizing two resistors. You’ll see it in each easy and superior circuits on a regular basis. Right here’s the essential setup:

The basic voltage divider circuit

It’s helpful for instance for studying sensors like thermistors and photoresistors because it converts an unknown resistance right into a voltage. Or to cut back the amount of an audio sign through a potentiometer.

You’ll find the output voltage by inserting the resistor values and the enter voltage into the next formulation:

V_{OUT} = frac{R2}{R1+R2} cdot V_{IN}

Or you should use the calculator just a little bit additional down on this web page.

As soon as you know the way it really works, it’s a lot simpler to see how circuits work. And it’ll allow you to calculate voltages at many alternative factors in a circuit – which is usually wanted to know it.

Voltage Divider Method

This formulation is likely one of the few electronics formulation (along with Ohm’s legislation) that I exploit frequently.

It’s for locating the output voltage when you have got two resistors related like this:

The basic voltage divider circuit

The formulation for calculating the output voltage is:

V_{OUT} = frac{R2}{R1+R2} cdot V_{IN}

This generally is a helpful formulation to recollect. It should come in useful usually. Or use the voltage divider calculator beneath when you desire the simple manner 😉

Voltage Divider Calculator

Fill within the enter voltage and resistor values within the voltage divider calculator beneath to seek out the output voltage:

Voltage Calculator Diagram

We’ve added this calculator to a sensible voltage divider calculator web page that you could bookmark and are available again to sooner or later.

The place Do You Discover The Voltage Divider?

One instance of a voltage divider circuit is for studying analog sensors. For instance, the thermistor is a temperature sensor. It adjustments its resistance based mostly on the temperature. In the event you join it with a recognized resistor worth in a voltage divider setup, you’ll get a voltage that is dependent upon temperature:

Voltage divider circuit with thermistor

Or you’ll be able to mix a recognized resistor with a photoresistor. The photoresistor adjustments resistance based mostly on the quantity of sunshine it detects. This fashion, you have got a circuit that will increase or decreases the voltage based mostly on mild.

Photoresistor sensor circuit

You may join the output of any of those circuits right into a comparator to verify it’s above or beneath a sure voltage. Then do one thing based mostly on that. For instance, if the temperature is above 40 levels, activate a fan.

Or join into an analog pin of an Arduino or a microcontroller and do cool stuff with it. Perhaps activate a light-weight if the photocell signifies that it’s darkish?

Calculation Instance: Completely different resistor values

Let’s say we now have the next values:




By utilizing the formulation above we get

V_{out} = frac{470 Omega}{180 Omega + 470 Omega} * 6 V = 4.3 V

Calculation Instance: Equal resistor values

Now, let’s say R1 and R2 has the identical worth.

V_{in} = 6 V

R_{1} = R_{2} = 470 Omega

By utilizing the formulation above we get

V_{out} = frac{470 Omega}{470 Omega + 470 Omega} * 6 V = 3 V

Because of this when the 2 resistors have the identical worth, the output is at all times half the enter.

Can You Use Voltage Divider as a Energy Provide?

In case you have a circuit that wants 4.5 V, might you employ a voltage divider with two 500 Ω resistors to get 4.5 V out of your 9V battery?

Sadly, it’s not that simple.

Any circuit you need to energy can have an inner resistance. So from the attitude of the voltage divider, no matter circuit you connect with the voltage output may be seen as a resistor (RLOAD) related in parallel with R2.

A circuit diagram with three resistors

If the inner resistance of the circuit (RLOAD) can be 500 Ω, what occurs?

Now, the R2 from the voltage divider formulation turns into the parallel resistance of R2 and RLOAD. Which is simply 250 Ω. In the event you put this into the voltage divider formulation, you get an output voltage of 3V as an alternative of the 4.5V you wished.

For an influence provide, you need the voltage to remain on the chosen degree irrespective of if the circuit you join has a excessive or low inner resistance. That’s why the voltage divider is just not generally used for energy provides.

As an alternative, you must use a voltage regulator.


What are your questions in regards to the voltage divider? Let me know within the remark part beneath.


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