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.
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.
