RC Filter & LC Resonance Calculator

Essential tools for audio, electronics, and communications projects

RC Filter Calculator

Calculate cutoff frequency or component values for RC high-pass and low-pass filters.

Low-Pass RC Filter
fc
Cutoff Frequency
159.15 Hz
Time Constant (τ)
1 ms
Capacitive Reactance at fc
1 kΩ
Attenuation at 10×fc
-20 dB

RC Filter Theory

  • Cutoff Frequency (fc) = 1 / (2πRC)
  • Time Constant (τ) = RC
  • Low-Pass Filter passes frequencies below fc, attenuates higher frequencies
  • High-Pass Filter passes frequencies above fc, attenuates lower frequencies
  • At the cutoff frequency, the output is -3dB (≈70.7%) of the input
  • Roll-off is -20dB/decade or -6dB/octave for first-order filters

LC Resonant Frequency Calculator

Calculate the resonant frequency of LC circuits for tuning and filtering applications.

LC Resonant Circuit
Resonant Frequency
15.92 kHz
Angular Frequency (ω)
100 krad/s
Period
62.8 μs
Quality Factor (Q)
--

LC Resonance Theory

  • Resonant Frequency (fr) = 1 / (2π√(LC))
  • Angular Frequency (ω) = 2πf = 1 / √(LC)
  • At resonance, inductive and capacitive reactances cancel (XL = XC)
  • LC circuits are used in tuning, filtering, and impedance matching applications
  • The quality factor (Q) depends on circuit losses (resistance)
  • Higher Q means sharper resonance and better frequency selectivity

Applications

  • Radio Tuners: Select specific frequencies from broadcast signals
  • Filters: Band-pass, band-stop, and notch filters
  • Oscillators: Generate stable frequencies
  • Impedance Matching: Maximize power transfer
  • Power Supplies: Reduce ripple in switching regulators