[sdiy] design experts

[Czech Martin]

Ok, I know some guys who have no "high level education",
i.e. a Ph. D. or M.S., but are very experienced, so
most of the time they can solve most problems.

So with a lot of experience you can get something without
too much theory.

But there are times when this is not enough.
If you have never thought about high frequency (i.e.
lumped elements do not hold, but traveling waves),
Maxwells equations (sounds scary, but can often be cooked
down to simple arangements where they are easy to solve,
gives good insight in capacitance, inductance and radiation
problems, coupling problems) and the like,
some problems remain "black magic" for ever.

Without solid theoretical background you have extreme
problems to understand and plan experiments, as well
as interpreting the results in such situations.

Example: some people do not know magnetic fields and inductance.
(I have to admit that I did not really understand in 
University. Now, after 12 years of more thinking I understand better).
They ask me for specs for output load "30pF".
So I keep telling them that:
-you need to take bondwire and PCB inductance into account
-you may need to model even a transmission line

but to no avail. They do not understand.

The outcome is that I/O drivers are overdimensioned,
which gives neat curves/rise time for a pure capacitive
load, but a "ringing" desaster for complex RLC impedances,
not to mention strip lines etc.

This is also unfortunate if the people who design PCBs are
only educated as draftsperson (?). So basically they do not
know what kind of disaster they are doing, the result is
very often a terrible S/N of the IC in system, where it is
good in our own design evaluation boards.


OTOH, "higher eduaction" without soldering is nothing.
I know enough Ph. D. guys who only did simulations (or worse).
They have a hard time when they start designing circuits.


You need really both sides.

In a job interview we try to find out if the person did solder (yes, diy!),
and what the theoretical skills are. The head of the analog group will
not employ any person without soldering background (can you tell how much W
this resistor has and what value it has is a likely question).
A M.S. is also required, but of course this depends on the field of where
the thesis work was done.

Currently there is a new breed of "designers" comming out, which are only
able to program HDL code. They do not know Ohm's law.
It is very hard to get allong with such people, because of this total
igorance. They are slaves of their tools (synthesis and P&R).
Not masters. 

And they produce systems that do not work.

Just look at this:

Why Johnnu can't design a high speed digital system

http://signalintegrity.com/Pubs/misc/whyjohnny.htm


m.c.