[time-nuts] Performance of 74LVC series ICs

Attila Kinali attila at kinali.ch
Mon Jun 1 12:59:18 EDT 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,
  permeability, resistivity,...)
* 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
  therma noise)
* 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.

> http://hyperphysics.phy-astr.gsu.edu/hbase/electronic/trangate.html

These are resistor-transistor-logic (RTL) elements. Those even more
noisy due to their simple build up.

			Attila Kinali

It is upon moral qualities that a society is ultimately founded. All 
the prosperity and technological sophistication in the world is of no 
use without that foundation.
                 -- Miss Matheson, The Diamond Age, Neil Stephenson

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