HOME  |  NEWS  |  BLOGS  |  MESSAGES  |  FEATURES  |  VIDEOS  |  WEBINARS  |  INDUSTRIES  |  FOCUS ON FUNDAMENTALS
  |  REGISTER  |  LOGIN  |  HELP
Comments
View Comments: Newest First|Oldest First|Threaded View
Jon Titus
User Rank
Blogger
Re: When Filters Deviate from Models
Jon Titus   5/15/2013 5:44:41 PM
NO RATINGS
Hi, AnalogBill.  I would assume that Microchip has taken non-ideal operations into consideration in the FilterLab software because the program uses Microchip op amps and the company wants engineers to get a good model so they will buy Microchip devices.  Good point, though, about watching out for models that do not reflect real-world op-amp characteristics.  Thanks for your comments.

Jon Titus
User Rank
Blogger
Re:Cost of software
Jon Titus   5/15/2013 5:41:54 PM
NO RATINGS
The Microchip software is free.

Analog Bill
User Rank
Gold
When Filters Deviate from Models
Analog Bill   5/8/2013 12:43:37 PM
NO RATINGS
Your filter plot highlights a common mistake in filter design. The deviation shown at 5 kHz on the plot may not be due just to the "protoboard" you used. Unless your modeling software contains a comprehensive model of the op-amps used, it may assume they're rather ideal ... especially with regard to gain-bandwidth or GBW. Since most filters, especially "anti-alias" filters, are useful because of their high attenuation beyond their cutoff frequency, this is an especially important consideration. Note that the first capacitor in each section has one end tied to an op-amp output. If the op-amp has infinite GBW, its output impedance will remain very low - even at high frequencies in the "cutoff region" of the filter's response. But if there's not enough GBW, this impedance will allow the first capacitor to feed signal around the stage, causing the "leveling out" of passband attenuation hinted at by the plot.

mtripoli3
User Rank
Silver
More software...
mtripoli3   5/7/2013 9:56:38 AM
NO RATINGS
Texas Instruments has a great filter design program called FilterPro Desktop. Incredibly well done and totally free (you will have to login to download). I've used it many times in the past; not only does it do "theoretical" but also has options for "real world" values. http://www.ti.com/tool/FILTERPRO

If you want something even more advanced and don't mind spending a few dollars ($49 to be exact) there is Filter Wiz Pro from Schematica. It's like the TI program on steroids (http://www.schematica.com/active_filters/fwpro.html). More choices for filter designs than you will ever need. 

The Microchip offering is good for what it costs (free) but you will find the other two much more useful as genuine tools.

AnandY
User Rank
Gold
Re:Cost of software
AnandY   5/7/2013 7:24:46 AM
NO RATINGS
Jon, thanks for the informative post. By entering our requirements, we will be provided with the filter design along with the schematic, component values, spice. Is this FilterLab software available for free download? If yes, then it will be a great help for self training projects.



Partner Zone
Latest Analysis
Design collaboration now includes the entire value chain. From suppliers to customers, purchasing to outside experts, the collaborative design team includes internal and external groups. The design process now stretches across the globe in multiple software formats.
Researchers have developed a hybrid energy harvester for generating electricity from multiple spectrums of solar energy.
A new high-pressure injection-molding technology produces near-net shape parts with 2-inch-thick walls from high-performance materials like PEEK, PAI, and carbon-filled polymers. Parts show no voids, sinks, or porosity, have more consistent mechanical properties, and are stronger.
These futuristic military robots will help soldiers and other military personnel better perform their duties.
Icon Labs has developed a whitepaper to help determine the type of cybersecurity needed based on the type of device.
More:Blogs|News
Quick Poll
The Continuing Education Center offers engineers an entirely new way to get the education they need to formulate next-generation solutions.
SEMESTERS: 1  |  2  |  3  |  4  |  5  |  6 |  7 | 8 | 9


Focus on Fundamentals consists of 45-minute on-line classes that cover a host of technologies. You learn without leaving the comfort of your desk. All classes are taught by subject-matter experts and all are archived. So if you can't attend live, attend at your convenience.
Learn More   |   Login   |   Archived Classes
Twitter Feed
Design News Twitter Feed
Like Us on Facebook

Technology Marketplace

Copyright © 2016 UBM Canon, A UBM company, All rights reserved. Privacy Policy | Terms of Service