Unloaded V_out
V_out = V_in × R2/(R1+R2)Loading page content...
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Professional voltage divider calculator with standard resistor values, tolerance analysis, loading effects, and multi-stage design. Calculate Vout, power dissipation, and impedance.
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Electronics & Circuit Design
Calculate output voltage, resistor ratios, current, power dissipation, and loading effects for precision circuit design.
Output Voltage
V_out = V_in × R2/(R1+R2)
Total Resistance
R_total = R1 + R2
Divider Current
I = V_in / R_total
Input Impedance
Z_in = R1 + R2
Reviewed by: CalculatorApp Electronics Engineering Team
A voltage divider is one of the most fundamental passive circuits: two resistors in series connected across a voltage source produce a lower output voltage at their junction. It is used for level shifting, sensor biasing, ADC input scaling, signal attenuation, and setting reference voltages in analog circuits. Understanding loading effects, Thevenin equivalents, and power ratings is essential for reliable design.
Unloaded V_out
V_out = V_in × R2/(R1+R2)Loaded V_out
V_out = V_in × (R2||R_L)/(R1+R2||R_L)Power (R1)
P1 = I² × R1 = (V_in-V_out)²/R1Thevenin R
R_th = R1 || R2| E-Series | Values per Decade | Tolerance |
|---|---|---|
| E6 | 6 preferred values | 20% |
| E12 | 12 preferred values | 10% |
| E24 | 24 preferred values | 5% |
| E96 | 96 preferred values | 1% |
1845: Gustav Kirchhoff formulates current and voltage laws, establishing the mathematical basis for resistive dividers.
1870s: Wheatstone bridge (an extended divider) becomes the standard for precision resistance measurement.
1900s: Potentiometers (adjustable voltage dividers) widespread in radio volume controls and signal calibration.
1950s: Bipolar transistor circuits use voltage dividers for base bias networks in amplifier design.
1970s: Op-amp virtual ground and gain-setting resistors apply voltage divider principles in integrated circuits.
Modern era: Precision thin-film resistor dividers achieve 0.01% accuracy in high-resolution ADC reference circuits.
Electronic circuit design standards from the Institute of Electrical and Electronics Engineers.
International standards for fixed resistors and tolerance series.
Precision electrical measurement standards and traceable references.
Workplace electrical safety standards for circuit design.
Myth: A voltage divider can power a load like a regulator.
Fact: Voltage dividers waste significant power and have poor regulation under load. Use a regulator IC for power delivery.
Myth: Output voltage is independent of the connected load.
Fact: Any load in parallel with R2 causes a loading error; lower load impedance causes larger error.
Myth: Tolerance does not matter for voltage dividers.
Fact: For precision applications, a ±1% tolerance on both R1 and R2 can result in ±2% total output error.
Myth: Higher resistor values are always better to save power.
Fact: Very high resistances make dividers sensitive to parasitic capacitance and input bias currents.
A voltage divider uses two series resistors to produce an output voltage that is a fraction of the input voltage: V_out = V_in × R2/(R1+R2).
When the load resistance is comparable to R2 (loading effect), the actual V_out drops below the unloaded formula prediction.
A low-impedance load in parallel with R2 reduces the effective lower resistance and pulls V_out down. The loaded V_out = V_in × (R2||R_L)/(R1 + R2||R_L).
Set the divider current (bleeder current) at least 10× the expected load current to minimize loading effect.
Z_in = R1 + R2. A high-impedance source requires high R values; a low-impedance load requires low R values.
No. Unregulated dividers waste power proportional to R1+R2. Use a linear regulator or DC-DC converter for power delivery.
An attenuator is an extended voltage divider designed to reduce signal level by a precise dB, used in RF and audio applications.
V_th = V_in × R2/(R1+R2) and R_th = R1||R2. This connects the divider to load analysis and amplifier input modeling.
Resistor values drift with temperature (ppm/°C). Use matched resistors with identical temperature coefficients for precision dividers.
E12 provides 12 preferred values per decade (e.g., 10, 12, 15, 18, 22…27…33…39…47…56…68…82) with ~10% tolerance.
Only for very light loads. For stable reference voltages, use a dedicated voltage reference IC (e.g., LM4040, REF02).
P = V²/R or P = I²R for each resistor. Choose parts rated at least 2× the calculated power for reliability.
Combine voltage divider with Ohm\'s law, motor sizing, and wavelength calculators for full electronic system design.
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