Hugh,

I didn t say it was bad to rely on simulations.
Everything that could help you to do your job better
and saves time is good to be used.
If you are good at it, go on. I believe all you say is
true. Even a teacher (considered here as the most
stupid person) could learn a lesson by hard after
repeating it several times a day. 
What I would say is if I d spent 20 years on
simulating, I d have started dreaming the results
before even starting the simulation. 
Or maybe I m getting you wrong? Maybe each  time you
simulate completely different circuit and you never go
back to modify the old one? When people talk about
simulations they mean simulating the schematics. Don t
you think that the layout is also an important part of
the designing process?
 IMO to be a good designer is not the same as to be
good in using some tools like PSPICE (for example). As
well as to be a good PCB designer has nothing to do
with how good you are on using Protel or any other
tool. It s a way of thinking that makes the
difference. Knowledge and experience are more
important for me. All the rest we call "supporting
tools". They could make your life easier but can t do
the job instead of you.

Whatever I say seems to hurt somebody. Why don t you
just accept different people might have different
points of view?

Mira
--- Hugh Stevenson <[EMAIL PROTECTED]> wrote:
> Good designers rarely simulate their circuitry???
> 
> Perhaps 20 years on I am still a newbie!
> 
> I find simulation a great tool checking stability of
> control loops,
> finding the optimum resistor for damping, finding
> out the effect of
> parasitic inductance and capacitance, calculating
> noise gain of
> preamps...  I rarely build a lashed up prototype
> these days.  Its not
> usually possible anyway as everything needs a ground
> plane and
> components are too small to modify easily!
> 
> If you find simulations taking you too long, get
> some training to use
> them better.  I can simulate things between about 10
> and 100 times
> faster than building them, and they don't catch fire
> (important for
> power supply work).  They have to be built in the
> end but my
> understanding is usually much better than if I had
> just done a rough
> design and built it.
> 
> Cheers, Hugh.
> 
> -----Original Message-----
> From: Mira [mailto:[EMAIL PROTECTED]] 
> Sent: Sunday, June 30, 2002 10:11 AM
> To: Protel EDA Forum
> Subject: Re: [PEDA] SPICE sim question
> 
> 
> Nice and true thoughts, Gary.
> It all depends on:
> 1. How experienced you are when doing and debugging
> your designs.
> 2. How experienced you are with the simulation
> tools.
> Mainly analog specialists go for this.
> Good designers rarely simulate their circuitry,
> while
> newbies start with it to see the effect of changing
> the circuitry and the values.
> As opposed to what was already said, I can say that
> simulations cannot replace the real world. They are
> helpful, yes, but only if you know what you are
> doing. Otherwise they
> may put you in a wrong direction. As for the time
> you'll need to do this
> job... it depends on you. I've seen people spending
> months for
> simulations and then twice more time for debugging. 
> Luckily there are still bosses, who may afford to
> pay
> for it.
> 
> Mira
> --- Gary Packman <[EMAIL PROTECTED]> wrote:
> > 
> > 
> > Afshin Salehi wrote:
> > > 
> > > Just out of curiosity, what types of things do
> you
> > guys run simulations on?
> > 
> > Amplifiers, linear and switching power supplies,
> > filters, and just about
> > anything else that will need tweaking on the
> bench.
> > 
> > > What drives you to run a simulation on that
> > specific device?
> > 
> > Testing for stability, what range of component
> > values (tolerance) will
> > work reliably, gain, rolloff, keeping signal
> levels
> > away from the rails
> > when designing high gain multi-stage amplifiers,
> and
> > most important of
> > all, gaining rapid insight into what happens when
> > you go outside the
> > box.  Also, nothing catches fire or explodes in a
> > simulator!
> > 
> > >How accurate is the simulation to a real world
> > bread boarded device?
> > >
> > Once you learn how to use simulation I would say
> > about 98% accurate, but
> > there is a giant proviso here, you must have
> > accurate models and you
> > must understand the limitations of the simulation
> > process.  I cannot
> > remember the last time a finished product did not
> > behave as the
> > simulation did.  The more often you simulate, the
> > better you and your
> > results get.
> > 
> > > Jon Elson said it takes a day at first then
> maybe
> > an hour or so each time to
> > > remember things, how is that justified to your
> > boss?  I am really just
> > > curious as to what things people run sims on,
> how
> > complex those circuits
> > > that are simulated are, and if the tests are
> worth
> > while?
> > > 
> > I use an old but very capable DOS version ($15,000
> > when new) of PSPICE.
> > I can hand type an ASCII circuit description page
> in
> > about a half-hour
> > (three or four op-amps and twenty or thirty
> passive
> > parts).  Another
> > twenty minutes to patch typos and missed
> > connections. After the circuit
> > is running you can do a number of tests in minutes
> > that would take a
> > week on the bench.  Whether it is worth the
> trouble
> > or not all depends
> > on what you're doing.  The last thing I did was a
> > strain gauge amplifier
> > (something I never did before).  Had the circuit
> up
> > and running in one
> > afternoon, cost of components about $10 versus a
> > packaged product with
> > similar specs from Omega for $400.  Is that
> > worthwhile?  My boss thought
> > so.  
> > 
> > It all depends...
> > Gary Packman
> > 
> > > Thanks,
> > > 
> > > Afshin
> > > 
> > >
> >
>
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