Home Filter manual [0101] [Filt] [Math] [Pwr] Examples Utilities
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4th order:
Bessel (pink)
Butterworth (cyan)
Chebyshev (red)
inverse Chebyshev (blue)
Cauer (green)

Welcome to what would be my homepage. It's made with the thought of hosting a sort of a "universal filter" for LTspice, some power electronics models (and not only) for aid in simulating large-scale schematics at block-level, rather than element-level, and a few other utilities.

Filter manual

What I affectionately call Filter is a library containing subcircuits of analog and digital filters. There are more details inside the manual (see the link in the menu) but, in a few short, descriptive words, the Filter holds the following: -3dB/octave and Bessel (analog only), Butterworth, Chebyshev, inverse Chebyshev and Cauer/Elliptic (analog and IIR), plus FIR filters with windows such as rectangular, Hann, Hamming, Blackman, Kaiser, Dolph-Chebyshev, but also pulse-shaping Gaussian, raised cosine and root-raised cosine, differentiator and Hilbert transformer. Almost all support low-pass, high-pass, band-pass and band-stop, some also all-pass.
Since LTspice is a dedicated analog circuit simulator, the digital filters are, of course, built in an analog way, limited by the "engine": no N bits quantizing and transients may suffer from spikes or sample distortions. Of course, digital also means speed penalty for time domain so don't think that now you can quickly see an 8th band parametric equalizer or a multistage interpolating filter. You may get lucky, you may not (more likely not). The analog filters may also have a few issues, but generally minor ones. Still, the Filter supports both time- and frequency-domain analysis and the usage should come in handy for anyone.
However, I'm only human, so mistakes are possible. Should any be found, please don't hesitate to let me know that I might correct them. I sometimes visit the LTspice Yahoo group (registration required to avoid spam), but not always as I am not lurking the Internet too often. Or you could drop a mail at imbvlad at gmail, I'll respond as quickly as I see the mail.

The manual can be freely downloaded in a single archive as either a zip or a 7-zip file, or from the LTspice Yahoo group file section. The symbol, Filter.asy, and the subcircuit file, filter.sub, are inside the archive, in ./html/files/, along with all the examples, or separate (the online version doesn't have the files). Any updates brought to the Filter are usually added to the manual, as well, so when a new major change appears, the archives will be updated, as well; no need for separate downloads. If minor changes occur, though, an archived version of the stand-alone files will be uploaded.

Download the files here (as of 29-march-2015): Zip archive: Filter_Manual.zip (192922 B) 7z archive: Filter_Manual.7z (74383 B)
Only the [symbol+library] (the directory structure is shown inside the archive), 6-dec-'15: Zip archive: Filter.zip (75135 B) 7z archive: Filter.7z (33257 B)
Only the examples from the manual and the [symbol+library] for those who want to browse the manual online (extract the contents into Filter_Manual/html/., so there will be Filter_Manual/html/files/ folder afterwards): Zip archive: files.zip (101660 B) 7z archive: files.7z (38432 B)

0101, Filt, Math, Pwr

The other libraries are from various domains. The [0101] includes some digital ADC, DAC, counter (all up to 16 bit), binary to decimal and reverse (which are, basically, the same as ADC/DAC only at unscaled, fixed levels), plus a JK flip-flop. [Filt] has, among others, an AGC, dead-time and dead-zone, frequency and phase meters, integrator and differentiator, PID/PI/PD (/ID/P) controller, 1st/2nd/3rd order SISO state-space, PLL. [Math] has some LTspice native functions available as one- or two-variable blocks, only built in a more stream-lined manner. Finally, [Pwr] holds some power-related functions, mostly three-phase, such as 3-level modulation, harmonics generator, space-vector HCC and PWM, Clarke and Park matrices, symmetrical components extractor, etc. Almost, if not all, are built in an idealized manner, as simple as possible, to make simulation at block level possible without the speed penalty. It also allows for replacing a specific ideal block with a real-life case schematic, while not having such an impact on performance. I, for one, found them useful. I hope you do, as well.
More about them in the four square-bracketed entries in the top menu.


In Examples there are a few schematics mainly regarding power conditioning, pq and dq theories, active power filters and such. They are built with models from the four libraries as a sort of a showcase, but not with this specific emphasis.


The Utilities entry in the top menu hosts two files: a syntax highlighting .lang file and a color theme matching LTspice's, both of them made for text editors that use GtkSourceView under the hood (such as gEdit, Mousepad, Scribes).

Please consider that, even though they are not large files and the bandwidth is quite generous, it's not unlimited; it would be better and faster to simply download the archive(s) rather than browsing them online. The files, as they are on my hard-disk, are virus/spyware/malware/etc-free, but I cannot guarantee that the files, once they have left my computer, aren't affected in any way. Simply opening up the archives and viewing the list of the files inside is harmless on any computer.

©Vlad, 2014 - 2015