Voltage Divider Calculator | Resistor Voltage Calculator with Unit Conversion

Voltage Divider Calculator

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Voltage Divider Formula:

Vout = Vin × (R2 / (R1 + R2))

Voltage Divider Circuit Diagram

Vin R1 R2 Vout Current (I)

The voltage divider circuit consists of two resistors (R1 and R2) connected in series with an input voltage (Vin). The output voltage (Vout) is measured between R2 and ground.

Comprehensive Guide to Voltage Dividers

What is a Voltage Divider?

A voltage divider is a fundamental electronic circuit that produces an output voltage (Vout) that is a fraction of its input voltage (Vin). It consists of two passive elements (typically resistors) connected in series, with the output voltage taken from the connection point between them.

How Voltage Dividers Work

The voltage divider operates based on Ohm's Law and the principle of series circuits:

  • The same current flows through both resistors (I = Vin/(R1 + R2))
  • The voltage drops across each resistor proportional to their resistance
  • The output voltage is the voltage drop across R2
  • No current flows through the output in an ideal circuit (infinite impedance load)

Practical Applications

Voltage dividers are used in numerous electronic applications:

Application Description
Sensor Interfaces Convert variable resistance (thermistors, photoresistors) to voltage signals
Reference Voltages Create precise voltage references for analog circuits
Signal Attenuation Reduce signal amplitude to match input requirements
Biasing Circuits Set operating points for transistors and amplifiers
Potentiometers Variable voltage dividers for volume controls, etc.

Unit Conversion Reference

Unit Symbol Multiplier Base Unit Equivalent
Millivolt mV 10-3 0.001 V
Volt V 1 1 V
Kilovolt kV 103 1000 V
Milliohm mΩ 10-3 0.001 Ω
Ohm Ω 1 1 Ω
Kilohm kΩ 103 1000 Ω
Megohm MΩ 106 1,000,000 Ω
Gigohm GΩ 109 1,000,000,000 Ω

Practical Example

Scenario: You need to power a 3V device from a 9V battery using a voltage divider.

Solution:

  1. Choose R1 = 10kΩ and R2 = 5kΩ
  2. Calculate Vout = 9V × (5kΩ / (10kΩ + 5kΩ)) = 3V
  3. Verify power dissipation: PR1 = (9V-3V)²/10kΩ = 3.6mW
  4. Check if resistors can handle the power (standard 1/4W resistors are sufficient)

Note: This is for illustration only. In practice, voltage dividers aren't ideal for powering devices due to loading effects.

Design Considerations

When designing with voltage dividers:

  • Loading Effects: The connected load should have impedance >> R2 to avoid significant voltage drop
  • Power Dissipation: Calculate power (P = V²/R) to ensure resistors can handle it
  • Current Draw: Lower resistor values draw more current but are less affected by loading
  • Precision: Use 1% or better tolerance resistors for accurate voltage division
  • Temperature Effects: Consider resistor temperature coefficients for precision applications

Advanced Topics

Non-Resistive Dividers: Voltage dividers can also use reactive components:

  • Capacitive dividers for AC signals
  • Inductive dividers in transformer applications
  • Complex impedance dividers for frequency-dependent circuits

Loaded Voltage Dividers: When a load is connected, the equivalent parallel resistance of R2 and Rload must be used in calculations:

Vout = Vin × (R2 || Rload) / (R1 + (R2 || Rload))

Where || represents parallel resistance: R2 || Rload = (R2 × Rload)/(R2 + Rload)