Potential Dividers: Sharing Voltage
Learn how to easily obtain a fraction of a voltage source using simple resistors.
What is a Potential Divider?
A potential divider (or voltage divider) is a simple passive linear circuit that produces an output voltage (V_out) that is a fraction of its input voltage (V_in). It’s incredibly useful when you need to step down a voltage without using a complex power supply, or when you need a variable voltage.
The Principle and Formula
The core idea is based on Ohm’s Law and series circuits. When two resistors (R1 and R2) are connected in series across a voltage source (Vin), the voltage is divided between them in proportion to their resistance values. The output voltage is typically taken across one of the resistors. The formula for the output voltage (V_out) across R2 is:
V_out = V_in * (R2 / (R1 + R2))
This formula shows that if R2 is larger relative to R1, a larger portion of the input voltage will appear across R2. If R1 is larger, more voltage will drop across R1, leaving less for R2.
Interactive Potential Divider
Adjust the input voltage and resistor values to see the output voltage change in real-time.
Conceptual Diagram
Calculated Output Voltage:
— VApplications of Potential Dividers
Potential dividers are simple yet versatile, appearing in many electronic designs:
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Volume Controls: A potentiometer (a variable resistor) acts as a potential divider to adjust the audio signal level.
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Sensor Circuits: Many sensors (like light-dependent resistors or thermistors) change their resistance based on environmental conditions. When placed in a potential divider, the output voltage changes, allowing a microcontroller to read the sensor data.
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Voltage Scaling: To safely connect a higher voltage signal to a circuit designed for lower voltages (e.g., a 5V microcontroller input connected to a 12V sensor output).
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Biasing Transistors: Setting the correct operating point for transistors in amplifier circuits often uses potential dividers.
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