Voltage Divider Simulator
Simulate Vout, current, power, and load effects
Voltage Divider Formulas
| Quantity | Formula | Meaning |
|---|
| Output voltage | Vout = Vin x R2 / (R1 + R2) | Ideal output voltage without a load. |
| Loaded bottom resistance | Rbottom = R2 || RL | R2 in parallel with the load resistor. |
| Loaded output | Vout = Vin x Rbottom / (R1 + Rbottom) | Output voltage after load effect. |
| Power | P = V^2 / R = I^2R | Used to check resistor wattage. |
Practical Rules
- A larger R2 compared with R1 gives a higher output voltage.
- A low-value load resistor can pull Vout down significantly.
- Lower total resistance increases current draw and wasted power.
- Use power results to choose resistors with enough wattage margin.
Example: Vin = 12 V, R1 = 1 kOhm, and R2 = 2 kOhm gives Vout = 8 V before loading.
Step-by-Step Example
With Vin = 12 V, R1 = 1000 ohm, and R2 = 2000 ohm, the ideal output is Vout = 12 x 2000 / (1000 + 2000) = 8 V. The divider current is I = 12 / 3000 = 0.004 A, or 4 mA. If a load is connected, the simulator first combines R2 and RL in parallel, then recalculates the output voltage.
When to Use a Voltage Divider
- Create a lower reference voltage from a higher supply voltage.
- Scale a signal before an analog input, such as a microcontroller ADC pin.
- Estimate how much a sensor or load will change the expected output voltage.
Common Design Mistakes
- Ignoring the load resistance, which can make the real output lower than the ideal formula.
- Choosing resistor values that waste too much current.
- Using resistors without checking power dissipation and tolerance.
Frequently Asked Questions
What is a voltage divider?▼
A voltage divider uses two resistors in series to produce an output voltage that is a fraction of the input voltage.
What is the voltage divider formula?▼
Without load, Vout = Vin * R2 / (R1 + R2).
What does a load do?▼
A load resistor appears in parallel with R2, lowering the effective bottom resistance and usually lowering Vout.
Why simulate power?▼
Power helps check whether resistor wattage ratings are sufficient and whether the divider wastes too much current.
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