RE: Potential Contributions

Kev.,
 
Interesting stuff.  I didn't have time to read it
all, but these seem to be working as zero ohm
resistors (i.e. ideal shorts), but not as voltage
sources (generating current from some other form
of energy).  I wonder, if someone built a
generator from superconducting coils, would
that machine work as an ideal source?  I know,
this is way off the original topic, so I don't
mind if the answer came in a private message.
 
Going back to the original topic, it seems to me
that if there were two or more ideal sources in
parallel with perfectly identical voltages assigned
to them, the simulator's action should be to remove
all but one, and not to add resistors.
 
The reasoning I would give is that by definition an
ideal voltage source will carry as much current as
needed to maintain its voltage.  This could go all
the way to infinity.  Adding two infinite numbers
is still infinite as far as I know, so removing
the additional sources will still yield infinite.
They are simply not needed in the circuit...
 
Arpad
======================================================

________________________________

From: edaorg@v-ms.com [mailto:edaorg@v-ms.com] 
Sent: Wednesday, January 31, 2007 12:35 AM
To: verilog-ams
Cc: Muranyi, Arpad
Subject: Re: Potential Contributions


Muranyi, Arpad wrote: 

	Can't resist not to chime in...
	 
	Since when are physical devices ideal?  I.e. when will 
	a real life voltage source have zero impedance?  Let
	me know if you see one, I would like to get one of those.

Superconductors.

In particular: Josephson Junction logic circuits rely on switching the state of a SQUID from superconducting to resistive states; in the superconducting state the SQUID is an ideal 0V source - it switches to resistive when you drive too much current through it or apply a large enough magnetic field.

Here are some links :

 http://swordfish.eecs.berkeley.edu/markj.www/COSLGate.html
 http://books.google.com/books?id=8_mngdg77sUC&pg=PA300&lpg=PA300&dq=josephson+junction+%22voltage+state%22+logic&source=web&ots=pFt5FKyaFe&sig=4SvM-ZtRuw77AFK5hdBqNPKsZ3s#PPP1,M1


	 
	Also, believe it or not, 0.3+0.6 is NOT equal 0.9!!!
	Try this in Matlab:  isequal(0.3+0.6,0.9), the answer
	will be a FALSE.  The point is that if the voltage
	sources are defined using equations, you may get
	inequalities without noticing...

I'm aware of that, but the cases I'm considering (as likely) are those where some identical components have been instantiated in parallel and the voltage is more likely derived from parameters  (or zero for switches), so rounding error mismatch is not likely.

Kev.

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