In electronics, a voltage divider or resistor divider is a design technique used to create a voltage (Vout) which is proportional to another voltage (Vin).
Two resistors are connected as shown in Figure 1. The output voltage, Vout is related to Vin 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 Vout), that resistance must be considered in parallel with R2 (see: resistor) to determine the voltage at Vout.
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.
- Calculator: voltage divider - loaded and open circuit (http://www.sengpielaudio.com/calculator-voltagedivider.htm)