Enter Circuit Values
Impedance Response Graph
This graph uses a logarithmic frequency sweep around the calculated resonant frequency.
Example Data Table
| R | L | C | Frequency | Voltage | Expected Result |
|---|---|---|---|---|---|
| 1 kΩ | 50 mH | 10 µF | 225 Hz | 12 V RMS | Near resonance, high impedance |
| 470 Ω | 10 mH | 1 µF | 1.59 kHz | 5 V RMS | Balanced branch reactance |
| 2.2 kΩ | 100 mH | 100 nF | 1 kHz | 24 V RMS | Inductive or capacitive check |
Formula Used
Angular frequency: ω = 2πf
Inductive reactance: XL = ωL
Capacitive reactance: XC = 1 / ωC
Parallel admittance: Y = 1/R + j(ωC - 1/ωL)
Impedance: Z = 1 / Y
Resonant frequency: f₀ = 1 / 2π√LC
Parallel quality factor: Q = R√(C/L)
The calculator first converts all units to base units. Then it calculates branch admittance. The total admittance is inverted to get complex impedance. Current and power values use RMS voltage.
How To Use This Calculator
- Enter the resistor value and choose its unit.
- Enter the inductor and capacitor values with correct units.
- Enter the operating frequency of the circuit.
- Enter RMS voltage when current and power values are needed.
- Press the calculate button.
- Review impedance, phase, admittance, resonance, and branch currents.
- Use CSV or PDF export buttons to save results.
Parallel RLC Circuit Impedance Guide
Core Meaning
Parallel RLC impedance describes how a resistor, inductor, and capacitor behave when they share the same two nodes. The same voltage appears across every branch. Each branch draws a different current, so the total current depends on admittance. This calculator uses that idea. It converts each component into conductance or susceptance. Then it inverts total admittance to find impedance.
Why Parallel Impedance Matters
Parallel RLC circuits appear in filters, tuned amplifiers, power networks, sensors, and matching stages. At resonance, inductive and capacitive susceptance cancel. The input impedance becomes close to the resistor value. Away from resonance, the network can act inductive or capacitive. That change affects phase, current, power factor, and signal strength.
Practical Design Notes
Always enter RMS voltage when you need RMS current and power. Use the exact frequency that drives the circuit. Small component tolerances can shift resonance, especially in high Q networks. A large resistance gives a narrow bandwidth. A lower resistance increases damping and widens the response. Real inductors also have winding resistance. Real capacitors include loss. For final hardware, compare these ideal results with measured data.
Reading The Results
The real part of impedance represents resistive behavior. The imaginary part shows reactive behavior. A positive impedance angle means the network looks inductive. A negative angle means it looks capacitive. The current angle uses the opposite sign. The admittance graph helps you see how impedance changes with frequency. The peak impedance usually appears near resonance.
Use In Learning And Testing
Students can use this tool to verify manual work. Technicians can estimate branch currents before testing a board. Designers can compare resonance, bandwidth, and quality factor before choosing parts. Export options also help keep records. The CSV file is useful for spreadsheets. The PDF file is useful for reports. Recalculate after changing one value. This makes trends easier to understand and reduces mistakes.
Common Checking Steps
Start with example values. Confirm that resistance, inductance, capacitance, frequency, and voltage units are correct. Check the resonance value before reading phase. Compare branch currents with total current. If a result looks extreme, inspect very small capacitance or inductance entries. Tiny values can create very large reactance quickly often.
FAQs
1. What is parallel RLC impedance?
It is the equivalent opposition of a resistor, inductor, and capacitor connected across the same two nodes. It is found by adding admittances first, then taking the reciprocal.
2. Why does this calculator use admittance?
Parallel branches share voltage, so branch currents add directly. Admittance links voltage to current. That makes admittance the cleanest method for parallel RLC calculations.
3. What happens at resonance?
At ideal resonance, inductive and capacitive susceptance cancel. The input admittance becomes mostly conductance, and the impedance magnitude reaches a high value.
4. Why is impedance complex?
Complex impedance shows both magnitude and phase. The real part represents resistance. The imaginary part represents energy storage from inductance or capacitance.
5. What does a negative phase mean?
A negative impedance phase usually means the circuit looks capacitive. Current leads voltage in that case. A positive phase usually indicates inductive behavior.
6. Are real components perfectly ideal?
No. Real inductors have winding resistance. Real capacitors have loss and leakage. This calculator uses ideal formulas, so measured results may differ slightly.
7. What voltage should I enter?
Enter RMS voltage for AC circuit work. RMS voltage gives useful current and power results. Peak voltage would produce peak current instead.
8. Can I export the result?
Yes. Use the CSV button for spreadsheet work. Use the PDF button for printable summaries and simple electrical reports.