Table of Contents
What Is a Voltage Divider?
A voltage divider is a simple circuit consisting of two resistors in series across a voltage source. The output voltage taken across the lower resistor (R2) is a fraction of the input voltage. It is one of the most fundamental circuits in electronics, used for biasing, level shifting, and sensor interfaces.
The circuit works by splitting the input voltage proportionally between the two resistors according to their ratio. The output is loaded-sensitive, meaning connecting a load across R2 changes the output voltage unless the load impedance is much higher than R2.
Voltage Divider Formula
Applications
- ADC Input Scaling: Reduce a higher voltage signal to the 0-3.3V or 0-5V range accepted by microcontroller ADC inputs.
- Biasing: Set the DC operating point for transistor amplifiers.
- Potentiometers: A potentiometer is a variable voltage divider.
- Sensor Reading: Convert resistance changes (thermistors, photoresistors) to voltage changes.
Frequently Asked Questions
Does the load affect the output?
Yes. The load resistance appears in parallel with R2, reducing the effective R2 and lowering the output voltage. For minimal error, the load impedance should be at least 10x R2.
Can I use a voltage divider as a power supply?
Generally no. Voltage dividers have poor load regulation. Any change in load current changes the output voltage. Use a voltage regulator instead for power supply applications.
How do I choose resistor values?
Choose values that are large enough to minimize power waste but small enough to be much less than the load impedance. Typical values range from 1k to 100k ohms for signal circuits.