High/Low-Pass filter calculations

[Matttcattt]

Im planning to build some active filters. Searching the web came up with the perfect document - The SLOA093 ap note from TI on active filter design. One simple question. What units do the calculations use? Farads and Ohms right? I dont want to buy components 1,000,000 time too large.

 

[12 Cents]

What units do the calculations use? Farads and Ohms right? I dont want to buy components 1,000,000 time too large.

I think it assumes just Farads and Ohms. Of course you can enter Millifarads, but be sure to treat the result as Milliohms

 

[Matttcattt]

Thanks. I just wanted to get a second opinion.

 

[rpapps]

Filter Calcs

Hi Matttcattt
The calculations are intended for basic units ie. ohms, farads and hertz. Just use the appropriate multiplier when entering your component values.
Eg. 100 pF = 100 x 10 to -12 power, 0.1 mF = 0.1 x 10 to -6 power, 1k ohm = 1 x 10 to +3 power, 10 KHz = 10 x 10 to +3 power. You get the idea?
Hope this helps.
Cheers
Rob

 

[Matttcattt]

Thanks.

I dont like standard form (1x10^-6F). I prefer long decimals (0.000001F).

 

[pinkmouse]

You could try the sim on National's website, Webbench, it uses real world values.

 

[Evan Shultz]

TI also has a rather powerful program called FilterPro that will automate much of this for active filters. You can choose topology and choose some components while allow the rest to be auto-selected. I'd check it out.

 

[thomas997]

TI also has a rather powerful program called FilterPro that will automate much of this for active filters. You can choose topology and choose some components while allow the rest to be auto-selected. I'd check it out.

I agree, simple and easy to work with.

Here is the link: http://www-s.ti.com/sc/techzip/slvc003.zip

 

[Matttcattt]

I've already calculated the values and ordered the parts now, but I'll have a look anyway.