LC Butterworth Filter Calculator

This calculator calculates the capacitor and inductor values for an LC Butterworth filter for a given order up to 10. The results are based on scaled prototype filters.

LC filters are typically used for higher frequencies - the mega Hertz range. For audio filters check out our active filter calculators.

3dB Frequency (MHz)
Terminating Resistance Ohms
Filter Order
First Component CapacitorInductor

Prototype filters with cut off at 1rad/sec and resistor of 1 ohm:

Here are the prototype Buterworth filter elements -

N
1 2.0000
2 1.4142 1.4142
3 1.0000 2.0000 1.0000
4 0.7654 1.8478 1.8478 0.7654
5 0.6180 1.6180 2.0000 1.6180 0.6180
6 0.5176 1.4142 1.9319 1.9319 1.4142 0.5176
7 0.4450 1.2470 1.8019 2.0000 1.80191.2470 0.4450
8 0.3902 1.1111 1.6629 1.9616 1.9616 1.6629 1.1111 0.3902
9 0.3473 1.0000 1.5321 1.8794 2.0000 1.8794 1.5321 1.0000 0.3473
10 0.3129 0.9080 1.4142 1.7820 1.9754 1.9754 1.7820 1.4142 0.9080 0.3129

Filter scaling equations:

C'=(R/R')(w/w')*C

L'= (R'*R)(w/w')*L

Where the ' designates the new desired filter characteristics.

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