4th Order Butterworth Filter

[KHzKid]

Hi all, I have a 100 KHz square wave and I'd like to utilise a low pass filter to filter out all the harmonics and leave just the fundamental. Leaving me with a 100 KHz sinusoid.

A fourth order Butterworth looks ideal for this but I'm struggling with the maths. Please can somebody show me how to calculate the capacitor/resistor values?

Thanks for any help!

 

[crutschow]

Download this software from TI Active Filter Design Application - FILTERPRO - TI Software Folder. It does the math for you and can generate filters from 1 to 10 poles.

Be aware that even a 4th order filter will not generate a perfect sinewave from a squarewave.

 

[KHzKid]

That's great, thanks! I wish I had asked sooner now lol