Digital circuits and analog devices
ard.p850ug1 at gmail.com
Thu Dec 1 23:59:16 CST 2016
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
(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'
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