Voltage Divider Calculator

Understanding Voltage Dividers

What is a Voltage Divider?

A voltage divider is a simple circuit that produces an output voltage that is a fraction of its input voltage. It consists of two resistors connected in series, with the output taken from the connection point between them.

Formula

The output voltage is calculated using:

V_out = V_in × (R₂ / (R₁ + R₂))

Where:

• V_in = Input voltage
• V_out = Output voltage
• R₁ = Top resistor (between V_in and V_out)
• R₂ = Bottom resistor (between V_out and ground)

Common Applications

• Sensor interfacing: Scaling sensor voltages to match microcontroller input ranges
• Reference voltages: Creating specific voltage levels for circuits
• Audio volume controls: Reducing signal levels
• Battery voltage monitoring: Scaling down high voltages for measurement
• Logic level conversion: Stepping down voltage levels between different logic families

Example Calculation

Given: V_in = 12V, R₁ = 10kΩ, R₂ = 10kΩ
V_out = 12 × (10k / (10k + 10k)) = 12 × 0.5 = 6V
With equal resistors, the output is exactly half the input!

Important Considerations

• Load effect: Connecting a load to V_out will reduce the output voltage
• Power dissipation: Both resistors will dissipate power as heat
• Current draw: Lower resistance values = higher current and power consumption
• Accuracy: Use precision resistors for accurate voltage division
• Impedance: High impedance loads (like voltmeters) won't affect the output

Choosing Resistor Values

For most applications, resistor values between 1kΩ and 100kΩ work well. Higher values reduce power consumption but can be more susceptible to noise. Lower values draw more current but are more stable with varying loads.