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

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(Created page with 'Q: What are the different LTspice file types? A: Schematic: name.asc the drawing with your circuit Symbol: name.asy symbols for the schematic Logfi…')
 
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Q:  What are the different LTspice file types?
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'''Q:''' What are the different LTspice file types?
 
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A:
 
 
     Schematic:    name.asc  the drawing with your circuit
 
     Schematic:    name.asc  the drawing with your circuit
 
     Symbol:        name.asy  symbols for the schematic
 
     Symbol:        name.asy  symbols for the schematic
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Q:  How can I add intrinsic device models (BJTs, FETs, etc.) to LTspice?
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'''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 section "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.
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'''A:''' You WILL find many answers when you search the messages for words like library, symbol or FAQ.
  
 
     Please read first the programs help:
 
     Please read first the programs help:
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     Files > Tut > Symbol Types For Subcircuits
 
     Files > Tut > Symbol Types For Subcircuits
  
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 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."
  
  
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]
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'''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]
  
  
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.  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.     
 
     PULSE(0 5 0 100p 100p 20n 100n)
 
     PULSE(0 5 0 100p 100p 20n 100n)
 
Don't use steeper transitions as required by your application.
 
Don't use steeper transitions as 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.
+
'''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.  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 -> compression" pane as well, but this setting will be lost after a new invocation of LTspice.
 
It could be switched off in the "Control Panel -> compression" pane as well, but this setting will be lost after a new invocation of LTspice.

Revision as of 06:16, 7 August 2009

Q: What are the different LTspice file types?

   Schematic:     name.asc   the drawing with your circuit
   Symbol:        name.asy   symbols for the schematic
   Logfile:       name.log   infos and results from .four, .measure, .op 
   Netlist:       name.net   you don't care about 
   Result:        name.raw   usually a binary file
   Result:        name.fft   result of an FFT, usually a binary file
   Plot settings: name.plt 
   Model file:     abc.xyz   contains the models, any file name  
   Symbol:        name.cir   if you have a netlist input file


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".


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.

   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: 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."


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. [1]


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 have to specify Trise and Tfall if you want a certain value.

   PULSE(0 5 0 100p 100p 20n 100n)

Don't use steeper transitions as 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 after a new invocation of LTspice.