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From: jeff@abnji.UUCP (jeff)
Newsgroups: net.analog
Subject: re: Electronics wearing out
Message-ID: <692@abnji.UUCP>
Date: Fri, 14-Jun-85 09:28:47 EDT
Article-I.D.: abnji.692
Posted: Fri Jun 14 09:28:47 1985
Date-Received: Sat, 15-Jun-85 07:47:08 EDT
Lines: 43
Keywords: reality, efficiencies, EPROMS, EEPROMS

[Resistance Is Useless!!! (if less than 1 ohm) ]

	The concept of electronics lasting forever is in the same
thinking that gives us never-dulling razor blades, 1000mpg, etc.
Reality creeps in everywhere, even in semiconductor devices.
You see, the devices aren't 100% efficient.  That's why they generate
heat.  If you use a device anywhere near its capacity, it will simply
wear out.  A usual tradeoff is speed & efficiency vs power & lifespan.
Underrating components will seem to make them last longer, but
usually will increase the cost immensely (ie a 5W transistor used for
4W won't last as long as a 100W transistor used for 4W, but doesn't
cost as much either.  The 100W transistor might be too inefficient
for use in the 4W circuit due to increased losses!).  Even
Consumer's Reports show that those 'bulb savers' cause a 100W bulb
to consume 60W of power but give the equivalent of 40W of light
although they last longer.  The tradeoff is that your manual labor
to replace the bulb may be worth the inefficiencies.
In computers, speed is of the essence.  Many critical components
are used to their maximum performance, such as using TTL
components to their maximum fanout (some EEs even exceed the current
rating with full knowledge that the device will need occasional
replacing but the performance is worth it).


	I remember that EPROMS and EEPROMS (aka EAPROMS) have a
finite number of cycles before the layer that is supposed to be
an insulator looses its insulating property.  You see, we want
to move electrons through the top layer when programming so it
acts as a poor conductor but all the rest of the time we want an
insulator that won't allow the electrons to wander around.  EPROMS
use UV light to scatter the electrons and give them the energy
to penetrate the top layer and fill all the cells.  Those UV lights
are rather strong, so the top layer (I forgot the technical term for
that layer)can be rather strong and lasts a long time.
EEPROMS need to be faster to program and react to an electrical signal
to provide erasure/programming.  This means a weaker layer and a
lower number of erase cycles (~10,000).  This is far from
forever!


			Jeff 'definitely an EE for today' Skot
			at the unmistakable ATT IS Atrium, Somerset NJ
			{ihnp4 | mcnc | cbosgb} abnji ! jeff