How to generate triangle shape?

Question

I tried to follow docs, and here is my implementation for triangle pulse:

V1 0 1 PULSE(-0.75 0.75 0m 8.335m 8.335m 0 16.67m 0)

but the result is:

although the Rise time is 8.335m at appears as 0, can someone explain what’s the issue?

Can you explain what kind of triangle pulse you want to generate and why the result isn't working for you? — Voltage Spike, Jul 18 '19 at 19:09
A triangle like in here: https://www.electronicspoint.com/forums/resources/simulating-sawtooth-and-triangular-waveforms.58/ — simo, Jul 18 '19 at 19:32

score 1 · Accepted Answer · answered Jul 18 '19 at 19:41

1

Don't ask why, but probably it NGspice fails simulating with a pulse width of 0.

The following will work:

V1 0 1 PULSE(-1V 1V 0 {8.335m-0.5n} {8.335m-0.5n} 1n {16.67m+1n} 0)

EDIT
It seems a known issue: https://sourceforge.net/p/ngspice/bugs/355/

Are you aware of the fact that setting a (pulse) parameter to 0 does not mean that it becomes 0.000000... but that SPICE sees this as a don't care and substitutes it with something (what it thinks is) reasonable? I would expect your actual pulse-width becomes 5 or 10% of the period (I didn't consult the source code for the exact number).

answered Jul 18 '19 at 19:41

Huisman

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Thanks! that was very useful :) – simo Jul 18 '19 at 19:47
I'm using LTspice a lot and was aware of such issues. See e.g. https://electronics.stackexchange.com/questions/237108/ltspice-default-rising-falling-times-of-pulse-edges – Huisman Jul 18 '19 at 19:51
Yea, I can see that, thank you – simo Jul 18 '19 at 19:59

How to generate triangle shape?

1 Answers1