Re: It's Official... PSpice Schematics v10.3!

From: Kevin Aylward (salesEXTRACT_at_anasoft.co.uk)
Date: 11/16/04 

Date: Tue, 16 Nov 2004 19:51:12 GMT

Ken Smith wrote:
> In article <8d-dnYBBBpESAgTcRVn-2g@comcast.com>,
> Joel Kolstad <JKolstad71HatesSpam@Yahoo.Com> wrote:
>> "Ken Smith" <kensmith@green.rahul.net> wrote in message
>> news:cnboan$vgl$1@blue.rahul.net...
>>> For sim. I use LTSpice. For product schematics, I use Orcad for
>>> DOS. For me, Spice is mostly about checking my math.
>>
>> It must take you a long time to do worst case analysis (i.e., Monte
>> Carlo simulation) by hand. :-)
>
> But that isn't "worst case". The real worst case is that all the
> parts are at the worst extreme that the maker allows to be shipped to
> the customer they like the least. ie: the parts I will actually get
> in production.

Yes, this is one definition of WC, the one I use, and of course, SS does
this automaticaly with a couple of button presses in the GUI.

The other definition is when components have been adjusted to give the
max/min voltages and currents, which is not the same, but you hope they
are.

>
> It takes surprising little time to do a real worst case check on a
> circuit.

If its done in a simulator, indeed. Doing it by hand is essentially,
impossible. You cant even get a closed form solution for a general 1
transister circuit, let alone one with 50 or 1000 of the buggers.

> In a good design there is always a safety margin so all you
> have to do is prove that there is still some margin not the exact
> amount it will be.

Well, absolute proof is not possible. A WC may be 3 or 6 standard
deviations from the norm. There is always a probability of violations of
these limits. Not everything is tested and culled to its stated limit.

>
> Spread sheets calculate fairly quickly even under Windoz.
>

Ahmmm...

Kevin Aylward
salesEXTRACT@anasoft.co.uk
http://www.anasoft.co.uk
SuperSpice, a very affordable Mixed-Mode
Windows Simulator with Schematic Capture,
Waveform Display, FFT's and Filter Design.

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