LC Filter Calculator

An LC filter is a circuit that uses an inductor (L) and capacitor (C) together to pass or block specific frequency ranges — used in audio electronics, RF design, and power supplies. Select your filter type (Low Pass, High Pass, or Band Pass) and what you want to calculate (Cutoff Frequency, Inductance, or Capacitance), then enter your known component values to get the cutoff frequency, along with inductance, capacitance, inductive reactance (XL), and capacitive reactance (XC).

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Cutoff Frequency

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Inductance

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Capacitance

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Inductive Reactance (XL)

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Capacitive Reactance (XC)

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Frequently Asked Questions

What are filter circuits?

Filter circuits are electronic circuits designed to allow certain frequencies to pass through while blocking others. They use components like inductors (L) and capacitors (C) to create frequency-selective networks that can filter out unwanted signals.

How do you calculate the cutoff frequency of an LC filter circuit?

The cutoff frequency of an LC filter is calculated using the formula fc = 1/(2π√LC), where fc is the cutoff frequency in Hz, L is the inductance in henries, and C is the capacitance in farads. This formula applies to both low-pass and high-pass LC filters.

What is the difference between low-pass and high-pass LC filters?

A low-pass LC filter allows frequencies below the cutoff frequency to pass while blocking higher frequencies. A high-pass LC filter does the opposite, allowing frequencies above the cutoff to pass while blocking lower frequencies. The component arrangement determines the filter type.

What inductor do I need for a 1 kHz LC low pass filter?

The required inductance depends on your chosen capacitor value. For example, with a 100nF capacitor, you would need approximately 253µH for a 1kHz cutoff frequency. Use the calculator to find the exact values for your specific requirements.

How do LC band-pass filters work?

LC band-pass filters combine both low-pass and high-pass characteristics to allow only a specific range of frequencies to pass through. They use resonant LC circuits that have maximum response at the resonant frequency and attenuate frequencies both above and below this point.

What is reactance in LC circuits?

Reactance is the opposition to current flow in AC circuits. Inductive reactance (XL = 2πfL) increases with frequency, while capacitive reactance (XC = 1/(2πfC)) decreases with frequency. At the cutoff frequency, XL equals XC in LC filters.

How do I choose component values for my LC filter?

Start by determining your desired cutoff frequency, then choose either an inductor or capacitor value based on availability and cost. Use the calculator to find the corresponding component value. Consider factors like component tolerance, size, and current/voltage ratings for practical implementation.

What are the advantages of LC filters over RC filters?

LC filters offer no power dissipation (ideal components), sharper roll-off characteristics, and better performance at high frequencies. However, they are typically larger, more expensive, and may have issues with component tolerances and parasitics compared to RC filters.