Difference between revisions of "Most frequently asked questions for beginners"

From LTwiki-Wiki for LTspice
Jump to navigationJump to search
Line 3: Line 3:
 
  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  infos and results from .four, .measure, .op (text file viewable from within LTspice)
+
Netlist:      name.net  unprocessed netlist (text file viewable from within LTspice & usable by other SPICE engines)
Netlist:      name.net  intermediate text file netlist (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), any file name
+
  Model file:    abc.xyz  text file containing model(s) - may be any valid file name
  Symbol:       name.cir  frequently used extension for an external netlist input file (text)
+
  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 on "Copy" in the tool bar. Select what you want to copy. Make the other schematic active and then click on "paste" in the tool bar.
+
'''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 ASCII-text. Merge the text as described in message 7201 in the Yahoo Group. [http://tech.groups.yahoo.com/group/LTspice/message/7201?threaded=1&l=1]
+
'''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 "Files > Lib".
+
'''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 WILL find many answers when you search the messages for words like library, symbol or FAQ.
+
'''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 group.
+
  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. Default value: 10% of Ton or 10% of Tperiod-Ton whatever is smaller. You have to specify Trise and Tfall if you want a certain value.     
+
'''A:'''  LTspice automatically will use a default value for <trise> and <tfall> if these parameters are set to zero.&nbsp; Default value: 10% of Ton or 10% of Tperiod-Ton whatever is smaller.&nbsp; 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.
Line 56: Line 57:
 
'''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. 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.
+
'''A:'''  LTspice has waveform compression enabled as the default setting.&nbsp; This compression reduces the amount of saved data during the simulation.&nbsp; It's a lossy compression and thus it can distort the saved signals.&nbsp; 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 -> compression" pane as well, but this setting will be lost upon closing the current session of LTspice.
+
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.