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Filter Wizard and Capacitor Values

Question asked by AnneM Employee on Feb 27, 2017
Latest reply on Dec 7, 2017 by FleetFoot

From blog post - Active Filter Design in a Snap - Analog Filter Wizard 

 

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Hi,

 

Great tool and I have used it a lot...but...I find one nasty issue. My filter design is low frequency, and the solution keeps coming up with capacitor values like "750nF" and "910nF". Sorry, no values like this available from any supplier I know!

An option that allows you to enter the cap values *closest* to what you can find, and displays the results, would be on my wish list.

 

Also, did someone change the program? On low frequency circuits, and since last time I used it, it appears to be scaling caps to 10x what they previously were, and adjusting resistors down.

 

Thanks,

Gary

 

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Gary,

 

Filter Wizard, by default, uses E24 series values for capacitors and E96 value for resistors.

E-series of preferred numbers - Wikipedia 

 

If you're having trouble finding E24 capacitor values, you can switch to a lower E-series in the "Component Tolerances" tab of the tool:

 

 

Regarding the 10x scaling for the capacitors in Filter Wizard - I'm not aware of any change that would result in a change in the R/C scaling.  Do you have any example download packages that show this issue?

 

One thing to keep in mind - There are three ways to "optimize" your design in Filter Wizard.  These three optimizations all result in different default R/C scaling.  

 

Regards,

-Anne

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