Bandpass Filter Calculator
Computes resonant frequency, bandwidth, and Q factor from an RLC circuit's component values. In a series RLC the resonator presents minimum impedance at f₀; in a parallel RLC it presents maximum impedance. Useful for verifying IF filter designs and LC tank circuits.
Equations & Parameters ▸
\(f_0 = \dfrac{1}{2\pi\sqrt{LC}}\qquad Q_{series}=\dfrac{\omega_0 L}{R}\qquad Q_{parallel}=\dfrac{R}{\omega_0 L}\)
| L | Inductance of the resonator. |
| C | Capacitance of the resonator. |
| R | Series resistance (series RLC) or parallel resistance (parallel RLC) in Ω. |
| f₀ | Resonant frequency = 1/(2π√LC). |
| Q | Quality factor. Series: Q = ω₀L/R. Parallel: Q = R/(ω₀L). |
| BW | −3 dB bandwidth = f₀/Q. |
Physical constants used
| c | Speed of light = 2.998×10⁸ m/s |
| µ₀ | Permeability of free space = 4π×10⁻⁷ H/m ≈ 1.2566×10⁻⁶ H/m |
| ε₀ | Permittivity of free space = 8.854×10⁻¹² F/m |
Inputs
Ω
Results
Resonator
Resonant frequency, f₀—
Q factor—
−3 dB bandwidth—
Band edges
Lower −3 dB, f₁—
Upper −3 dB, f₂—
Diagram