[sdiy] measuring pulse width with ns accuracy...

[Magnus Danielson]

From: Michael Buchstaller <buchi at takeonetech.de>
Subject: Re: [sdiy] measuring pulse width with ns accuracy...
Date: Mon, 21 Apr 2003 01:31:09 +0200

> >i didn't try it with a true oscilloscope, just spice. but I figured that
> >if it didn't work in spice, it probably won't work in reality either... ?
> 
> Many circuits behave different in Spice than in reality. Sometimes
> circuits use odd behaviour of parts (e.g. 4069 mis-used as Op-Amp),
> and such things seem not to work in spice, but will in real-world.
> On the other hand, simulation can fool you the other way round, too.

Like all tools, it has its limits and you really must understand these and
be sure they don't stab you in the back. As for the 4069 example, you must use
the correct Spice model. If you use a model which has sufficient detail about
the innards, i.e. with the FET-transistors, Spice would probably be fairly
accurate. If you only use a digital gate model you would be out in the blue.

*ANY* simulation is not better than the modeling of the real-life situation
that you think you are going to test. This includes component models, variations
in values and properties (heat), modeling of parasitics etc. etc. etc.
You also depend on the correctness of the simulation tool (shiver!).

Cheers,
Magnus