Duncan Wither

LTSpice

Info:

• .step param - steps throguh paramiter values. Reference
• .param - sets a parameter to a specific value.

Plotting non time information

• .measure allows you to retain the key info from each simulation.
• This outputs to the log.
• Right clicking these numbers on the logs lets you plot it.
• Reference

Comments

• You can use either of the insert text commands, and enure the comment radio button is selected.
• Alternatively you can prepend your spice directive with an * to convert it to a comment.
  • e.g. *.step param Voff -10 10 1 is ignored (instead of stepping through the parameter).
  • This is useful for selecting specific simulations to run on the same circuit quickly.

Parameters

• You can use parameters to more easily step through values
• Define parameters with a .param statement
  • Make sure it’s a spice directive, not a comment
• To use it in values (i.e. as a voltage or time etc.) use curly brackets
• You can run multiple simulations where you step through param values with .step
  • This will re-run the sim for each of the values given.
• Multiple .step statements will run one after the other, so every combination will occur.
  • To prevent this, and use pairs / triples use a table.

*Stepping:
.step oct param X 100u 100m 1 

*Table:
.step param X list 1 2 3 
.param IND=tab1e(X, 1, 14.7, 2, 9.1, 3, 0) 
-param RES=table(X, 1, 22700, 2, 47200, 3, 1G) 

Example usage:

Random Numbers

• This is for generating random numbers, useful in monte carlo simulaitons
• gauss(x); A random number from Gaussian distribution with a sigma of x
• flat(x); A random number between -x and x with uniform distribution
• mc(x,y);A random number between x(1+y) and x(1-y) with uniform distribution.

Coupled Inductors / Transformers:

• Use a K statement

Initial Conditions

• .ic sets initial conditions.
• Often useful for caps or inductors.
• .ic V(capv)={X} sets the net capv to the value of param X.
• see wiki and spiceman for more info.