LC Filter Calculator | Low Pass, High Pass, Band Pass | Resonance Frequency

📖 LC Filter Calculator

An LC filter uses inductors (L) and capacitors (C) to create frequency-selective circuits. This calculator helps you design low-pass, high-pass, and band-pass filters by calculating resonance frequency, cutoff frequency, impedance, and Q factor.

📐 LC Filter Formulas

Resonance Frequency: fo = 1 / (2π√(LC))
Characteristic Impedance: Zo = √(L/C)
Q Factor: Q = Zo / R
Low Pass Cutoff: fc = 1 / (2π√(LC))
Bandwidth: BW = fo / Q

📊 LC Filter Applications

Application	Type	Typical Frequency
RF Tuning	Band Pass	1 MHz - 1 GHz
Power Supply Filtering	Low Pass	10 Hz - 1 kHz
Audio Crossovers	Low/High Pass	100 Hz - 5 kHz
EMI/RFI Filtering	Low Pass	10 kHz - 100 MHz
Matching Networks	Band Pass	1 MHz - 1 GHz
Oscillator Tanks	Band Pass	1 kHz - 100 MHz

❓ Frequently Asked Questions

What is resonance frequency? ▼

Resonance frequency (fo) is the frequency where the inductive and capacitive reactances are equal. At resonance, the LC circuit has maximum impedance (parallel) or minimum impedance (series).

What is the characteristic impedance of an LC filter? ▼

Characteristic impedance Zo = √(L/C) is the impedance of the LC network. It's used to match the filter to source and load impedances for maximum power transfer.

What is Q factor? ▼

Q (Quality Factor) measures the selectivity of the filter. Higher Q means narrower bandwidth and sharper roll-off. Q = Zo / R, where R is the load resistance.

How do I choose L and C values? ▼

Use fo = 1/(2π√(LC)) to select L and C. For RF applications, use nH/µH inductors and pF capacitors. For audio, use mH inductors and µF capacitors.