Electrical Engineering Stack Exchange is a question and answer site for electronics and electrical engineering professionals, students, and enthusiasts. It only takes a minute to sign up.
Sign up to join this community
Is this possible to have perfect components in LTspice? No parasitic inductance, no parasitic capacitor, no resistor, etc? Is it not possible is it possible to make a model and model it with no parastic parameters?
I would like to have a perfect diode, perfect MOSFET, IGBT etc. Should I use another software for doing something like this?
If I not able to understand some phenomenoms with perfect components I won't be able to understand it with parasatic components.
LTspice solves nonlinear differential equations numerically. It's not an AI system that can figure out intelligently whether a diode is conducting or not, and thus solve your homework questions or whatever.
In general I think that models that are not "smooth" will cause convergence problems.
So a perfect resistor is fine, but a perfect diode would have to be approximated to the desired degree of accuracy by something like a arctangent function such that the diode current vs. voltage does not have an abrupt change.
A perfect capacitor or inductor would cause a singularity if you connected it to a voltage source or a current source respectively that changed instantly.
LTSpice tries to prevent you from making this mistake by helpfully ignoring you when you set rise and fall times to zero and using default values that are rather large. Similarly, the "switches" in LTspice and PSpice are made imperfect.
In a sense all components in LTSpice are ideal, but generally networks of them are used to simulate imperfect real components, with greater or lesser fidelity.
Sometimes the defaults give you imperfect components, but you can always override that by choice. It often helps to use perfect components in a first cut proof of principle circuit, before turning up the difficulty of making it work in the real world.
Some components in the real world tend to be so imperfect, parasitic series resistance in an inductor for instance, it makes sense always to include it. Resistors and capacitors OTOH, especially when used at low frequency, tend to be OK when ideal. We know we're dealing with an RF circuit when we have to start worrying about parasitics in Rs and Cs. In an RF circuit, we also worry about parasitics in connecting wires, the nets! These behave like transmission lines.
