Steven Philley
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Vol. IV — Electronics · Tool

Q-factor

Series or parallel RLC tanks. Change R, L, and C — f₀, Z₀, Q, bandwidth, and −3 dB band edges update as you type.

How it works

Resonant frequency f₀ = 1/(2π√(LC)) and characteristic impedance Z₀ = √(L/C) are the same for series and parallel tanks. Quality factor and −3 dB bandwidth swap with topology.

Series: Q = Z₀ / R, BW = f₀ / Q. Parallel: Q = R / Z₀, BW = f₀ / Q. Band edges ≈ f₀ ± BW/2 (good when Q ≫ 1). Ideal lumped parts — real ESR and coil Q trim these numbers.

Pair with LC resonance for f₀ alone, Impedance for |Z| at a chosen f, dB / dBm for ratios and levels, or Reactance for single-part X. Back to the electronics bench.