Calculator
This tool keeps the page in a single vertical flow. The input fields switch to a 3-column layout on large screens, 2 columns on medium screens, and 1 column on mobile.
Plotly Graph
The graph compares ideal output behavior with loaded output behavior across a sweep of input voltage. It updates after calculation.
Example Data Table
| Case | Mode | Vin | Primary Input | Load | Approx. Output | Approx. Attenuation |
|---|---|---|---|---|---|---|
| 1 | Attenuation dB | 12 V | 6 dB | 10 kΩ | 6.01 V ideal | 6 dB |
| 2 | Ratio | 9 V | Vin/Vout = 3 | Open | 3.00 V ideal | 9.54 dB |
| 3 | Target Output | 5 V | Vout = 2 V | 4.7 kΩ | 2.00 V target | 7.96 dB |
| 4 | Resistor Network | 24 V | R1 = 4.7 kΩ, R2 = 2.2 kΩ | 10 kΩ | 6.65 V loaded | 11.15 dB |
Formula Used
1) Voltage Ratio
k = Vout / Vin
2) Attenuation in Decibels
Attenuation(dB) = 20 × log10(Vin / Vout)
3) Ratio from dB
k = 10^(-Attenuation(dB) / 20)
4) Loaded Shunt Resistance
Rsh = (R2 × RL) / (R2 + RL) when a load is connected.
5) Loaded Divider Output
Vout = Vin × Rsh / (Rs + R1 + Rsh)
6) Power Checks
PR1 = I² × R1
PR2 = Vout² / R2
Pload = Vout² / RL
How to Use This Calculator
- Choose the calculation mode that matches your problem.
- Enter the input voltage and any source resistance.
- Add the load resistance if the attenuator feeds a real circuit.
- For dB, ratio, or target voltage modes, add a reference shunt resistor to generate suggested divider values.
- For direct network analysis, enter R1 and R2.
- Press the calculate button to show results above the form.
- Use the CSV or PDF buttons to export the calculated result table.
- Check the graph to compare ideal and loaded output behavior.
FAQs
1) What does attenuation mean in this calculator?
Attenuation is the reduction from input voltage to output voltage. The tool expresses that reduction as a ratio, percentage, and decibel value for easier circuit comparison.
2) Why does the loaded output differ from the ideal output?
A connected load sits in parallel with the shunt resistor. That lowers the effective shunt resistance and usually pulls the output voltage below the ideal no-load target.
3) When should I use attenuation in dB?
Use dB when you work with signal levels, instrumentation, audio circuits, communication paths, or design documents that already specify losses in decibels.
4) What does the ratio input represent?
The ratio field uses Vin divided by Vout. A ratio of 2 means the output is half the input. A ratio of 10 means the output is one tenth.
5) Why are resistor power values important?
Power values help you choose safe resistor wattage. If the calculated dissipation approaches the part rating, the resistor can overheat and drift or fail.
6) Can I leave the load resistance blank?
Yes. Leaving the load blank treats the output as open circuit. That is useful for estimating the ideal divider result before another stage is attached.
7) What is output impedance used for?
Output impedance helps predict how strongly the attenuator will interact with the next stage. Lower output impedance usually makes the output less sensitive to load changes.
8) Can this tool size a divider from a target output?
Yes. Use the target output, dB, or ratio modes and enter a reference shunt resistor. The calculator then suggests a matching series resistor and estimates loaded performance.