Electronics Toolbox

Voltage Divider Calculator

Using the Calculator

To calculate the Input Voltage enter Resistor R1, Resistor R2 and Output Voltage and click Calculate Values.

To calculate the Output Voltage enter Input Voltage, Resistor R1 and Resistor R2 and click Calculate Values.

To calculate the value for Resistor R1 enter Input Voltage, Resistor R2 and Output Voltage and click Calculate Values.

To calculate the value for Resistor R2 enter Input Voltage, Resistor R1 and Output Voltage and click Calculate Values.

What is a voltage divider?

A resistor voltage divider is a simple yet essential circuit used to reduce voltage and create reference voltages. It consists of two resistors connected in series across a voltage supply. The output voltage is taken from the junction of these two resistors. Here’s a detailed explanation of how it works:

Basic Principle

The voltage divider works on the principle of voltage drop across resistors in a series circuit. According to Ohm's Law, the voltage drop across a resistor in a series circuit is proportional to its resistance.

Voltage Divider Formula

The output voltage $$V_{out}$$ is given by the formula:

$$V_{out} = V_{in} \times \frac{R2}{R1 + R2}$$

Where:

• $$V_{in}$$ is the input voltage.
• $$R1$$ is the resistance of the first resistor.
• $$R2$$ is the resistance of the second resistor.
• $$V_{out}$$ is the output voltage.

Working Explanation

1. Total Resistance: The total resistance of the series combination is $$R1 + R2$$.
2. Current Through the Circuit: Since the resistors are in series, the same current $$I$$ flows through both resistors. Using Ohm's Law, the current is:

$$I = \frac{V_{in}}{R1 + R2}$$
3. Voltage Drop Across R1: The voltage drop across $$R1$$ (let's call it $$V_{R1}$$) is:

$$V_{R1} = I \times R1 = \frac{V_{in} \times R1}{R1 + R2}$$
4. Voltage Drop Across R2: The voltage drop across $$R2$$ (let's call it $$V_{R2}$$) is:

$$V_{R2} = I \times R2 = \frac{V_{in} \times R2}{R1 + R2}$$
5. Output Voltage: The output voltage $$V_{out}$$ is the voltage across $$R2$$, which is the same as $$V_{R2}$$:

Applications

1. Reference Voltage Generation: To provide a specific voltage level lower than the input voltage.
2. Signal Level Adjustment: To scale down signal voltages to appropriate levels for further processing.
3. Biasing Transistors: To provide necessary biasing voltages in transistor circuits.
4. Analog-to-Digital Converters (ADC): To create specific voltage levels for comparison.

Example Calculation

Suppose we have a voltage divider with $$V_{in} = 12V$$, $$R1 = 2k\Omega$$, and $$R2 = 3k\Omega$$.

Using the voltage divider formula:

$$V_{out} = 12V \times \frac{3k\Omega}{2k\Omega + 3k\Omega} = 12V \times \frac{3}{5} = 7.2V$$

Thus, the output voltage $$V_{out}$$ is 7.2V.