Owing to its popularity with students and electronics enthusiasts I am making a study of LTspice both for my own edification and to position myself to better assist participants on this and similar sites/lists...
Approaching LTspice, as I am, from an essentially 'OrCAD EE PSpice' background, I find myself 'navigating' the proverbial 'learning curve' in certain areas... Please do not perceive the following as a litany of complaints!!! In point of fact I am (pleasantly) surprised at LTspice's power and flexibility -- in any regard -- but especially as a gratis product! Moreover the veritable ubiquity of LTspice component models greatly enhances this already highly attractive platform!
The intent of this post is to verify bugs where present and learn the error of my ways where such is the case --- Again, this is in no way a 'put down' of LTspice!!! Trust me! OrCAD has more than a few 'proclivities' of its own!
So, here it goes...
RE: LTspice:
1) Transformers (i.e. inductors related via the mutual inductance "K" directive) do not simulate properly in the absence of inter-winding ohmic 'continuity'...
Example: The EMF plot of the 'hot' end of a grounded 'secondary' winding will be (wildly) erroneous or return a 'Singular Matrix' error, 'Floating Node' warning, etc... Unless the 'primary' is grounded (or otherwise ohmicly connected to the secondary)... As a side note, while reference to 'singular matrices' grants (welcome) insight into the modeling algorithm, it, sadly, throws little 'light' upon this aparent 'bug'...
2) MOSFETs do not 'simulate' well from threshold up to (but non-inclusive of) saturation --- Moreover subthreshold slope simulation is hopeless...
3) Apart from Zeners, the simulator does not support reverse breakdown characteristics...
4) Please advise me as to the native (or 'accepted') method of defining/modling inductor 'saturation'
Many advance thanks for any and all info, feedback and/or advice!
Best Regards
HP
Approaching LTspice, as I am, from an essentially 'OrCAD EE PSpice' background, I find myself 'navigating' the proverbial 'learning curve' in certain areas... Please do not perceive the following as a litany of complaints!!! In point of fact I am (pleasantly) surprised at LTspice's power and flexibility -- in any regard -- but especially as a gratis product! Moreover the veritable ubiquity of LTspice component models greatly enhances this already highly attractive platform!
The intent of this post is to verify bugs where present and learn the error of my ways where such is the case --- Again, this is in no way a 'put down' of LTspice!!! Trust me! OrCAD has more than a few 'proclivities' of its own!
So, here it goes...
RE: LTspice:
1) Transformers (i.e. inductors related via the mutual inductance "K" directive) do not simulate properly in the absence of inter-winding ohmic 'continuity'...
Example: The EMF plot of the 'hot' end of a grounded 'secondary' winding will be (wildly) erroneous or return a 'Singular Matrix' error, 'Floating Node' warning, etc... Unless the 'primary' is grounded (or otherwise ohmicly connected to the secondary)... As a side note, while reference to 'singular matrices' grants (welcome) insight into the modeling algorithm, it, sadly, throws little 'light' upon this aparent 'bug'...
2) MOSFETs do not 'simulate' well from threshold up to (but non-inclusive of) saturation --- Moreover subthreshold slope simulation is hopeless...
3) Apart from Zeners, the simulator does not support reverse breakdown characteristics...
4) Please advise me as to the native (or 'accepted') method of defining/modling inductor 'saturation'
Many advance thanks for any and all info, feedback and/or advice!
Best Regards
HP