Re: LT spice params

On Wed, 13 May 2009 10:26:15 -0700, Joerg
<notthisjoergsch@xxxxxxxxxxxxxxxxxxxxx> wrote:

Jon Kirwan wrote:
On Wed, 13 May 2009 07:42:54 -0700, Joerg
<notthisjoergsch@xxxxxxxxxxxxxxxxxxxxx> wrote:

Robert Baer wrote:
Joerg wrote:

John Larkin wrote:

On Tue, 12 May 2009 12:49:20 -0700, Robert Baer
<robertbaer@xxxxxxxxxxxx> wrote:

John Larkin wrote:

If I want to set Gmin, Abstol, or other LT Spice parameters, and have
them travel with a circuit model, how can I do this? Is there some
text thing I can include on a particular schematic that will set these
params for Spice? The LT Spice Simulation/Control Panel/Spice window
indicates that these settings are not inherently carried across
program invocations. Gmin of 1e-12 is just too leaky!

John


Use .PARAM or better yet .OPTIONS ??

Turns out you click the funny little letter icon, upper-right, and
then type

.OPTION Gmin=1e-18

Plop the resulting string somewhere on your schematic. That makes the
diodes work much better.


This shows up in the ascii netlist file as stuff like...

TEXT -600 -8 Left 0 !.option Gmin=1e-18
TEXT -608 32 Left 0 !.option abstol=1e-18
TEXT -608 72 Left 0 !.option chgtol=1e-18

It's been a while but IIRC you can also use ".option" just once,
followed by all the parameters you'd like to change, separated by spaces.

Careful with the computer. When doing stuff like this on a Pentium in
the 90's ... tsssk ... tick, tick, tick ... *PHUT* ... Pentium gone.

.OPTION CPU=AMD
:-)

As consultants we often have to take what's there at the clients offices.

That can sting a little, at times:

.OPTION CPU=IMSAI

IEEE Spectrum just had an interesting article about legacy chips that
made history, and the 8080 was at least mentioned (under 8088 which was
the real break-through).

http://www.spectrum.ieee.org/may09/8747

Yes. At the time, I was just going to college and was paying my own
way (no money within our family and I was the oldest.) I had read the
article on the Mark 8 Personal Minicomputer in Radio Electronics in
1974, but didn't feel ready/competent/money-flush to go for it at the
time. Then I saw the articles and ads that followed a little later in
Popular Electronics for the MITS ALTAIR 8800 and I went for it. Bought
the system (with just 256 bytes of memory) without a power supply or
any memory to fit the other three 256x8 static ram sockets on the main
board because I couldn't afford to add either. A simple power supply
was about my level of design skill as a hobbyist, so I did that part.
I also was being paid part time to solder probes for Tektronix to help
pay my way, so soldering I could also do. In no way was I prepared
for what happened when I finally splurged and later on (when they
became available) bought their 4k dynamic ram cards. They didn't
function and I was nearly in tears because of my lack of skill to do
more than solder them up. I spent the next 6-7 weeks learning and
eventually was able to work out the patches to make with the help of
someone's scope and the thoughts of the few friends in my age group
that I had at the time. In the process, I paid dearly in emotion but
also learned some digital and enough analog to actually do something
about the problems. I wouldn't put anyone through that, intentionally.
But in the end, I wound up having a story written about me in a
suburban, local newspaper which I didn't deserve but I suppose
happened more because at the time such things just didn't happen to
"regular folks," so it was a nice personal-interest story for them. I
don't know how they found out. But I just felt very embarrassed about
the whole thing.

I have very mixed feelings about that period. I suppose most of us do
about when we were just getting past the idea of being 18 years old,
though.

Jon
.

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