In electronics, a voltage divider or resistor divider is a design technique used to create a voltage (V_out) which is proportional to another voltage (V_in).

Resistor divider

Two resistors are connected as shown in Figure 1. The output voltage, V_out is related to V_in as follows:

As a simple example, if R₁ = R₂ then

Any other ratio between 0 and 1 is also possible.

Note that this rule only works if the divider is unloaded, that is, the load resistance is infinite and all of the current flowing through R₁ goes into R₂. If current flows into a load resistance (through V_out), that resistance must be considered in parallel with R₂ (see: resistor) to determine the voltage at V_out.

Figure 1: Resistor Divider

General impedance divider

A voltage divider is usually thought of as two resistors, but capacitors, inductors, or any combined impedance can be used. For general impedances Z₁ and Z₂, the voltage becomes

For instance, a divider with a resistor and capacitor:

will have voltage ratio:

since the capacitor's impedance is 1 / jωC (where j is the imaginary number, and ω is frequency in radians per second). The ratio then depends on frequency, in this case decreasing as frequency increases. This circuit is, in fact, a basic lowpass filter, or, in the world of audio, a treble-cut filter.

See also

• Potentiometer
• Wheatstone bridge

External links

• Calculator: voltage divider - loaded and open circuit (http://www.sengpielaudio.com/calculator-voltagedivider.htm)