[time-nuts] Performance of 74LVC series ICs
attila at kinali.ch
Mon Jun 1 16:59:18 UTC 2015
On Mon, 01 Jun 2015 11:00:31 -0400
Vlad <time at patoka.org> wrote:
> I am curious, how the integrated gates could be compared for those
> created on discrete elements ? Let say simple gates like this:
For the same implementation: Worse. There is much less control
over the exact building of discrete devices than integrated ones.
There hundreds of tiny things that are harder to control:
* You have wires going over the PCB. These have a long length, thus
a high inductivity, and high capacity.
* They are on a substrate that is known to be quite hydrophile and
thus has changing electrical parameters (dielectric constant,
* Everything is slower, due to higher capacitance/inductance/resistance
of the wires inbetween.
* Slower translates into less defined edges -> more jitter.
* Higher capacitance translates into more current flowing at the same
speed, which again translates into more shot-noise (though less
* Longer wires are more susceptible to EMI, or rather pick-up of tiny
interferences from other circuits or even other parts of the same
* Longer wires are also more prone to emit EMI.
... just to name a few. This list can be continued for quite some time.
On the other hand: A well designed discrete circuit can beat a general
purpose integrated circuit in almost all performance measures.
These are resistor-transistor-logic (RTL) elements. Those even more
noisy due to their simple build up.
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use without that foundation.
-- Miss Matheson, The Diamond Age, Neil Stephenson
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