Difference between revisions of "Most frequently asked questions for beginners"
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Schematic: name.asc the drawing with your circuit (a text file) | Schematic: name.asc the drawing with your circuit (a text file) | ||
Symbol: name.asy symbols for the schematic (a text file) | Symbol: name.asy symbols for the schematic (a text file) | ||
− | Logfile: name.log | + | Netlist: name.net unprocessed netlist (text file viewable from within LTspice & usable by other SPICE engines) |
− | + | Logfile: name.log info and results from .four, .measure, .op (text file viewable from within LTspice) | |
+ | may also contain the fully processed and expanded netlist (a [[Control Panel]] setting) | ||
Result: name.raw binary output data file (text format may be optionally specified) | Result: name.raw binary output data file (text format may be optionally specified) | ||
Result: name.fft binary result of an FFT | Result: name.fft binary result of an FFT | ||
Plot settings: name.plt text file used to save and restore Waveform Viewer plot settings | Plot settings: name.plt text file used to save and restore Waveform Viewer plot settings | ||
− | Model file: abc.xyz text file containing model(s) | + | Model file: abc.xyz text file containing model(s) - may be any valid file name |
− | + | Circuit file: name.cir frequently used extension for an external netlist input file (text) | |
'''Q:''' How do you copy and paste between schematics? | '''Q:''' How do you copy and paste between schematics? | ||
− | '''A:''' Click | + | '''A:''' Click the '''Copy Icon''' in the tool bar or select '''Copy''' from the '''Edit''' drop down menu (or type '''ctrl-C'''). Select (with the mouse) what you want to copy. Make the target schematic active (click on it or its tab or type '''ctrl-Tab''') and then click the '''Paste Icon''' in the tool bar or select '''Paste''' from the '''Edit''' drop down menu (or type '''ctrl-V'''). |
'''Q:''' How do I copy and paste between symbols in the symbol editor? | '''Q:''' How do I copy and paste between symbols in the symbol editor? | ||
− | '''A:''' It is not possible to use copy and paste in the symbol editor. Symbol files are | + | '''A:''' It is not possible to use copy and paste in the symbol editor. Symbol files are ascii text. Merge the text as described in [http://tech.groups.yahoo.com/group/LTspice/message/7201?threaded=1&l=1 message 7201] in the LTspice Yahoo Group. |
'''Q:''' How can I add intrinsic device models (BJTs, FETs, etc.) to LTspice? | '''Q:''' How can I add intrinsic device models (BJTs, FETs, etc.) to LTspice? | ||
− | '''A:''' Please take a look to the many examples in the section | + | '''A:''' Please take a look to the many examples in the files section of the LTspice Yahoo Group ([http://tech.groups.yahoo.com/group/LTspice/files/%20Lib/ Files => Lib]). |
'''Q:''' How can I add subcircuits to LTspice? | '''Q:''' How can I add subcircuits to LTspice? | ||
− | '''A:''' You | + | '''A:''' You will find many answers when you search the LTspice Yahoo Group messages for words like "library", "symbol" or "FAQ". |
Please read first the programs help: | Please read first the programs help: | ||
− | Help ->Schematic Capture -> Editing Components -> Creating New Symbols | + | Help -> Schematic Capture -> Editing Components -> Creating New Symbols |
Help -> Help Topics ->FAQs -> Third party models | Help -> Help Topics ->FAQs -> Third party models | ||
Help -> Help Topics ->FAQs -> Mosfet | Help -> Help Topics ->FAQs -> Mosfet | ||
− | You will find also help in the linked documents from our LTspice Yahoo | + | You will find also help in the linked documents from our LTspice Yahoo Group. |
Links | Links | ||
− | Links > Spice Courseware And Tutorials | + | Links -> Spice Courseware And Tutorials |
There is another document about symbols and models in our Files section. | There is another document about symbols and models in our Files section. | ||
− | Files > Tut > Symbol Types For Subcircuits | + | Files -> Tut -> Symbol Types For Subcircuits |
− | '''Q:''' I have a pulse source in my schematic with zero transition times. LTspice only shows slow transition times of 2ns. What's going on here? | + | '''Q:''' I have a pulse source in my schematic with zero transition times. LTspice only shows slow transition times of 2ns. What's going on here? |
PULSE(0 5 0 0 0 20n 100n) | PULSE(0 5 0 0 0 20n 100n) | ||
− | '''A:''' LTspice automatically will use a default value for <trise> and <tfall> if these parameters are set to zero. | + | '''A:''' LTspice automatically will use a default value for <trise> and <tfall> if these parameters are set to zero. Default value: 10% of Ton or 10% of Tperiod-Ton whatever is smaller. You must specify Trise and Tfall if you want a certain value. |
PULSE(0 5 0 100p 100p 20n 100n) | PULSE(0 5 0 100p 100p 20n 100n) | ||
Don't use steeper transitions than required by your application. | Don't use steeper transitions than required by your application. | ||
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'''Q:''' I have used a pure sine source in my schematic, but the output signal of my circuit looks slightly different from cycle to cycle. | '''Q:''' I have used a pure sine source in my schematic, but the output signal of my circuit looks slightly different from cycle to cycle. | ||
− | '''A:''' LTspice has waveform compression enabled as the default setting. | + | '''A:''' LTspice has waveform compression enabled as the default setting. This compression reduces the amount of saved data during the simulation. It's a lossy compression and thus it can distort the saved signals. You can switch it off with the following command line in your schematic. |
.options plotwinsize=0 | .options plotwinsize=0 | ||
− | It could be switched off in the "Control Panel -> | + | It could be switched off in the "Control Panel -> Compression" pane as well, but this setting will be lost upon closing the current session of LTspice. |
Revision as of 15:40, 17 August 2009
Q: What are the different LTspice file types?
Schematic: name.asc the drawing with your circuit (a text file) Symbol: name.asy symbols for the schematic (a text file) Netlist: name.net unprocessed netlist (text file viewable from within LTspice & usable by other SPICE engines) Logfile: name.log info and results from .four, .measure, .op (text file viewable from within LTspice) may also contain the fully processed and expanded netlist (a Control Panel setting) Result: name.raw binary output data file (text format may be optionally specified) Result: name.fft binary result of an FFT Plot settings: name.plt text file used to save and restore Waveform Viewer plot settings Model file: abc.xyz text file containing model(s) - may be any valid file name Circuit file: name.cir frequently used extension for an external netlist input file (text)
Q: How do you copy and paste between schematics?
A: Click the Copy Icon in the tool bar or select Copy from the Edit drop down menu (or type ctrl-C). Select (with the mouse) what you want to copy. Make the target schematic active (click on it or its tab or type ctrl-Tab) and then click the Paste Icon in the tool bar or select Paste from the Edit drop down menu (or type ctrl-V).
Q: How do I copy and paste between symbols in the symbol editor?
A: It is not possible to use copy and paste in the symbol editor. Symbol files are ascii text. Merge the text as described in message 7201 in the LTspice Yahoo Group.
Q: How can I add intrinsic device models (BJTs, FETs, etc.) to LTspice?
A: Please take a look to the many examples in the files section of the LTspice Yahoo Group (Files => Lib).
Q: How can I add subcircuits to LTspice?
A: You will find many answers when you search the LTspice Yahoo Group messages for words like "library", "symbol" or "FAQ".
Please read first the programs help: Help -> Schematic Capture -> Editing Components -> Creating New Symbols Help -> Help Topics ->FAQs -> Third party models Help -> Help Topics ->FAQs -> Mosfet You will find also help in the linked documents from our LTspice Yahoo Group. Links Links -> Spice Courseware And Tutorials There is another document about symbols and models in our Files section. Files -> Tut -> Symbol Types For Subcircuits
Q: I have a pulse source in my schematic with zero transition times. LTspice only shows slow transition times of 2ns. What's going on here?
PULSE(0 5 0 0 0 20n 100n)
A: LTspice automatically will use a default value for <trise> and <tfall> if these parameters are set to zero. Default value: 10% of Ton or 10% of Tperiod-Ton whatever is smaller. You must specify Trise and Tfall if you want a certain value.
PULSE(0 5 0 100p 100p 20n 100n)
Don't use steeper transitions than required by your application.
Q: I have used a pure sine source in my schematic, but the output signal of my circuit looks slightly different from cycle to cycle.
A: LTspice has waveform compression enabled as the default setting. This compression reduces the amount of saved data during the simulation. It's a lossy compression and thus it can distort the saved signals. You can switch it off with the following command line in your schematic.
.options plotwinsize=0
It could be switched off in the "Control Panel -> Compression" pane as well, but this setting will be lost upon closing the current session of LTspice.