# How to use a parametric value within PULSE voltage source in LTSpice?

I would like to use a parametric symbol for the period value of the PULSE component in LTSpice but so far I have been unsuccessful. currently my source is:

PULSE(-15 15 0 0.1e-6 0.1e-6 0.4e-6 1e-6)


And I would like to for example change number '6' into a parameter, so then I could change that parameter if I wanted to. I tried the following but it did not work:

.PARAM f=6
PULSE(-15 15 0 0.1e-{f} 0.1e-{f} 0.4e-{f} 1e-{f})


Any solution or workaround is appreciated.

• You can't directly modify just the exponent. The number parser won't work like that. Instead, use the available functions as part of an expression that computes the values. – jonk Oct 23 '19 at 13:09

What @jonk said is true, but you can "cheat" a bit by using a parametric divisor, something like this:

PULSE(-15 15 0 {0.1u/x} {0.1u/x} {0.4u/x} {1u/x})
.param x=1
.step param x list 1 10 1000


Alternately, you can make it a bit more readable by making the rest of the values parametric:

PULSE(-15 15 {td} {tr} {tf} {Ton} {T})
.param T=1u/x Ton=0.4*T tr=0.1*T tf=tr td=0 x=1


This is just one way of doing it.

• Thank you for the solution (: – Ams Oct 23 '19 at 18:53