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Sallen-Key

Forum Post: Re: Multiple feedback filter not matching filterpro design recommendation - please help.

Rick Downs - WEBENCH Design Center

Edward, The problem is likely parasitics working in tandem with the large feedback resistor values. As noted in the OPA4820 datasheet, the part really doesn't like impedances around it higher than a couple of kΩs - because at higher values, the parasitics really start to affect the bandwidth...

on May 10, 2010
Forum Post: Re: FilterPro 3.0 Bug with Chebychev 4th order filter

Rick Downs - WEBENCH Design Center

David, We have found and verified the root cause of the problem you reported. It is in the design equations for Sallen-Key lowpass and highpass component value calculations when gain is greater than 1. Basically, component values are calculated without accounting for gain > 1 and hence the designed...

on Aug 18, 2010
Forum Post: Re: resistor value and other question

Rick Downs - WEBENCH Design Center

Koray, When FilterPro first does a design, it uses exact resistor values (0%) - you can then change this by using the controls at the top right of the schematic screen: You can set both resistor and capacitor tolerances, and FilterPro will find the nearest standard value to match your design...

on Oct 27, 2010
Forum Post: Different R´s and C´s value with Filterpro 3.0 and 3.1 versions

Fernando Krouwel

Some weeks ago, I designed a low pass Sallen Key with v. 3.0 (E12 components) and it worked very well when builtt. Now, I updated filterpro to v. 3.1, entered the same specs, selected E12 components and the resulting R´s anc C´s are rather different than the previous version. For it...

on Nov 11, 2010
Forum Post: Help..Im stuck with designing a band pass filter with frequency range (20Hz - 500Hz)

Ahmad Jazlan

Hello everyone I want to design a Sallen & Key Butterworth filter with frequency range 20Hz to 500Hz, but im not sure if filling in the right parameters. Could you all please give me some guidance.. I entered the following parameters into filterPro: Gain A0 = 1 V/V = 0dB Centre Frequency...

on Jan 6, 2011
Forum Post: Re: Designing band pass filter using STLM358

Rick Downs - WEBENCH Design Center

Danny, Cross over distortion would cause distortion, but shouldn't affect center frequency. What's at work here is inadequate gain bandwidth of the op amp. I put your parameters into FilterPro and created a design - the design report is attached: (Please visit the site to view this file...

on Aug 9, 2011
Forum Post: -3dB phase and gain margin

Abhijit Pethkar

I was trying to design the 4th order low pass filter of Sallen Key architecture in FilterPro. I have ported the values from FilterPro to TINA software and tried to measure the -3dB gain margin and phase margin but found that both the margins are zero. which means that the closed loop system is just on...

on Nov 2, 2011
Forum Post: Arbitrary topology for each filter stage in FilterPro.

Stanislaw Leschinsky

Good day, ladies and gentlemens. Can I arbitrary select topology for each filter stage in FilterPro 3.1.0.23446 and how I do this? F.e. Sallen-Key for first stage and MFB for second stage of 4-th order LPF. Thank you for advise.

on May 2, 2012
Forum Post: Incorrect Q value in HPF?

matthew fortin

In the FilterPro Desktop version, I am designing a 3rd order Chebyshev 0.5dB 135kHz High Pass Filter with a stopband freq of 10kHz. For the first stage, it lists a Q = 0.5. Doesn't Q=0.5 mean 2 repeated real poles at Fo? Is this mistake or is there a reasoning behind this? Shouldn't this stage...

on Sep 13, 2012

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Browse by Tags

Forum Post: Re: Multiple feedback filter not matching filterpro design recommendation - please help.

Forum Post: Re: FilterPro 3.0 Bug with Chebychev 4th order filter

Forum Post: Re: resistor value and other question

Forum Post: Different R´s and C´s value with Filterpro 3.0 and 3.1 versions

Forum Post: Help..Im stuck with designing a band pass filter with frequency range (20Hz - 500Hz)

Forum Post: Re: Designing band pass filter using STLM358

Forum Post: -3dB phase and gain margin

Forum Post: Arbitrary topology for each filter stage in FilterPro.

Forum Post: Incorrect Q value in HPF?