Filters · resonance · reactance

⚡ RC / LC Circuits

Compute cutoff frequency and time constant of RC and RL filters with a live Bode magnitude plot, find LC resonance and characteristic impedance, and get capacitor/inductor reactance at any frequency.

RC filter

RL filter

LC resonance

Reactance at frequency f

Formulas: fc(RC) = 1/(2πRC) · τ = RC · fc(RL) = R/(2πL) · f₀(LC) = 1/(2π√LC) · Z₀ = √(L/C) · Xc = 1/(2πfC) · XL = 2πfL. The Bode plot marks the −3 dB point at fc; slope is ±20 dB/decade.