Electrical Circuits
Voltage Divider
A voltage divider uses two series resistors to produce an output voltage that is a fixed fraction of the input. The fraction is set by the lower resistor R2 divided by the total resistance. The formula assumes no significant load current; connecting a load in parallel with R2 reduces the output voltage, which is why a divider that must drive a load is usually buffered.
Voltage Divider
V_out = V_in × R2 ÷ (R1 + R2)
Variables and units
| Symbol | Quantity | Unit |
|---|---|---|
| V_out | Output voltage across R2 | V |
| V_in | Input voltage across the divider | V |
| R1 | Upper resistor | Ω |
| R2 | Lower resistor | Ω |
Conditions of application
Unloaded divider, or a load whose resistance is much larger than R2 so that it draws negligible current. Loading lowers the output.
Worked example
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Output voltage of a two-resistor divider and the current through it.