2 Dec
2016
2 Dec
'16
5:59 a.m.
On Fri, Dec 2, 2016 at 2:31 AM, Noel Chiappa <jnc at mercury.lcs.mit.edu> wrote:
So I have this memory of a set of law promulgated by
an engineer at DEC, one
of which was something to the effect that 'all digital circuits are made out
of analog devices'. However, my memory doesn't recall where I saw this, and my
Google-fu is not strong enough to turn it up. Can anyone help?
It's one of Don Vonada's laws. I am pretty sure I first read them in
'Computer Engineering', that book produced by DEC. I think the
original is 'Digital circuits are made from analog parts'
Another of the laws is 'There is no such thing as ground' which
(a) means voltmeters have 2 leads, so you can take whatever
you want as a reference
and
(b) all connections have impedance (the inductance is the important
bit in general) so even if you have 2 points connected to a wire you
call 'ground' they won't necessarily be at the same voltage all the time.
A related one, which I don't know if it was ever written down in an
official book (he told it to me in person) came from Professor M. V. Wilkes
'A digital circuit is like a tame animal. An analogue circuit is like a
wild animal. Every so often the tame animal goes back to the wild'
-tony
-tony
Noel