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It is possible to use .fra to analyze a filter, low pass for example

Carlos Delfino All Messages By This Member #152846 I'm reading about the existence of the .fra component that generates a "Bode" diagram for an SMPS. Would it be possible to use this same component to analyze some type of filter, a low pass for example? -- Carlos Delfino
Jim Wagner All Messages By This Member #152847 开云体育 spice already does that for frequency dependent linear networks. You do not need any special components. Jim Wagner toggle quoted message Show quoted text On Apr 2, 2024, at 9:19 PM, Carlos Delfino <consultoria@...> wrote: I'm reading about the existence of the .fra component that generates a "Bode" diagram for an SMPS. Would it be possible to use this same component to analyze some type of filter, a low pass for example? -- Carlos Delfino
Jim Wagner All Messages By This Member #152848 开云体育 Should have added “continuous” (e.g. not time-varying) as one of the criteria. ?This is the one that SMPS usually violates and needs special techniques ro analyze. Jim toggle quoted message Show quoted text On Apr 2, 2024, at 11:10 PM, Jim Wagner <wagnejam99@...> wrote: spice already does that for frequency dependent linear networks. You do not need any special components. Jim Wagner On Apr 2, 2024, at 9:19 PM, Carlos Delfino <consultoria@...> wrote: I'm reading about the existence of the .fra component that generates a "Bode" diagram for an SMPS. Would it be possible to use this same component to analyze some type of filter, a low pass for example? -- Carlos Delfino
Carlos Delfino All Messages By This Member #152849 As I'm learning how to use LTSpice, could you send me an example or an article I can read on how to do it? -- Carlos Delfino Em qua., 3 de abr. de 2024 às 03:24, Jim Wagner <wagnejam99@...> escreveu: toggle quoted message Show quoted text Should have added “continuous” (e.g. not time-varying) as one of the criteria.? This is the one that SMPS usually violates and needs special techniques ro analyze. Jim On Apr 2, 2024, at 11:10 PM, Jim Wagner <wagnejam99@...> wrote: spice already does that for frequency dependent linear networks. You do not need any special components. Jim Wagner On Apr 2, 2024, at 9:19 PM, Carlos Delfino <consultoria@...> wrote: I'm reading about the existence of the .fra component that generates a "Bode" diagram for an SMPS. Would it be possible to use this same component to analyze some type of filter, a low pass for example? -- Carlos Delfino
Jim Wagner All Messages By This Member #152850 开云体育 Look up in the Help for directives. I think it is .frequency ?(word “frequency” preceded by a period or dot) Jim toggle quoted message Show quoted text On Apr 2, 2024, at 11:29 PM, Carlos Delfino <consultoria@...> wrote: As I'm learning how to use LTSpice, could you send me an example or an article I can read on how to do it? -- Carlos Delfino Em qua., 3 de abr. de 2024 às 03:24, Jim Wagner <wagnejam99@...> escreveu: Should have added “continuous” (e.g. not time-varying) as one of the criteria.? This is the one that SMPS usually violates and needs special techniques ro analyze. Jim On Apr 2, 2024, at 11:10 PM, Jim Wagner <wagnejam99@...> wrote: spice already does that for frequency dependent linear networks. You do not need any special components. Jim Wagner On Apr 2, 2024, at 9:19 PM, Carlos Delfino <consultoria@...> wrote: I'm reading about the existence of the .fra component that generates a "Bode" diagram for an SMPS. Would it be possible to use this same component to analyze some type of filter, a low pass for example? -- Carlos Delfino
Tony Casey All Messages By This Member #152851 开云体育 On 03/04/2024 06:19, Carlos Delfino wrote: I'm reading about the existence of the .fra component that generates a "Bode" diagram for an SMPS. Would it be possible to use this same component to analyze some type of filter, a low pass for example? Unless your filter is non-linear, it is easier and orders of magnitude quicker to simply use .AC analysis. With this, you can also directly plot return loss and complex impedance by adding a .NET directive. Regards, Tony
Andy I All Messages By This Member #152853 Carlos asked for an example showing how to simulate and plot the Bode plot from a linear low-pass filter in LTspice. I realize everyone needs to start from the beginning, but it is surprising if you could not find a thousand examples already. But I uploaded an example simulation for you.? It is here: ? ? Files > Temp > Low-pass_example.asc ? ? /g/LTspice/files/Temp/Low-pass_example.asc Click on the link above to download it.? Or, go to the group's webpage, click "Files" in the menu on the left, then click "Temp" to go to the "Temp" subdirectory or folder, and you will find the file in that folder. To use it, open it in LTspice and click "Run".? When it is done (it should take less than a tenth of a second), click on the wire with the "Out" label, and you will see the Bode plot of the filter. An ".AC" analysis is the simplest kind to see Bode plots of linear filters. Read LTspice's Help, which comes with the program. LTspice comes with several example schematics in the folder "examples\Educational".? Many are .TRAN analyses but several are .AC and make Bode plots, without using ".FRA". Andy
Jim Wagner All Messages By This Member #152855 开云体育 Big error in my advice. .AC rather than .frequency. Sorry Jim toggle quoted message Show quoted text On Apr 3, 2024, at 5:03 AM, Andy I <AI.egrps+io@...> wrote: Carlos asked for an example showing how to simulate and plot the Bode plot from a linear low-pass filter in LTspice. I realize everyone needs to start from the beginning, but it is surprising if you could not find a thousand examples already. But I uploaded an example simulation for you.? It is here: ? ? Files > Temp > Low-pass_example.asc ? ? /g/LTspice/files/Temp/Low-pass_example.asc Click on the link above to download it.? Or, go to the group's webpage, click "Files" in the menu on the left, then click "Temp" to go to the "Temp" subdirectory or folder, and you will find the file in that folder. To use it, open it in LTspice and click "Run".? When it is done (it should take less than a tenth of a second), click on the wire with the "Out" label, and you will see the Bode plot of the filter. An ".AC" analysis is the simplest kind to see Bode plots of linear filters. Read LTspice's Help, which comes with the program. LTspice comes with several example schematics in the folder "examples\Educational".? Many are .TRAN analyses but several are .AC and make Bode plots, without using ".FRA". Andy
Carlos Delfino All Messages By This Member #152861 Thanks. I haven't yet had time to view each example that comes with LTspice, but I'm slowly becoming familiar with its universe. -- Carlos Delfino Em qua., 3 de abr. de 2024 às 09:04, Andy I <AI.egrps+io@...> escreveu: toggle quoted message Show quoted text Carlos asked for an example showing how to simulate and plot the Bode plot from a linear low-pass filter in LTspice. I realize everyone needs to start from the beginning, but it is surprising if you could not find a thousand examples already. But I uploaded an example simulation for you.? It is here: ? ? Files > Temp > Low-pass_example.asc ? ? /g/LTspice/files/Temp/Low-pass_example.asc Click on the link above to download it.? Or, go to the group's webpage, click "Files" in the menu on the left, then click "Temp" to go to the "Temp" subdirectory or folder, and you will find the file in that folder. To use it, open it in LTspice and click "Run".? When it is done (it should take less than a tenth of a second), click on the wire with the "Out" label, and you will see the Bode plot of the filter. An ".AC" analysis is the simplest kind to see Bode plots of linear filters. Read LTspice's Help, which comes with the program. LTspice comes with several example schematics in the folder "examples\Educational".? Many are .TRAN analyses but several are .AC and make Bode plots, without using ".FRA". Andy

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