> can someone tell me the frequency that a 74LS14 can work up to.
> regards

That's the sort of question where some people may suggest you try a simple
web search 1st before asking on list - this way about 10 people are liable
to spend research time and bandwidth telling you something that you could
easily find with the same effort using Google. I'd tend to agree with them
in general principle :-)

Also, the answer varies depending on your application as it depends on
capacitive load and some other factors.
Also, rise and fall are asymmetric so knowing exactly what the application
is will help in the limit.

However, the datasheet here


http://personal.telefonica.terra.es/web/x-robotics/downloads/datasheets/74LS14.pdf

will probably answer your question.

In summary, it says:

Output rise time is 5 to 22 nS with 15 pF load and 8 to 25 nS with 50 pF
load.
Fall time is 5/22 and 10/33 respectively.
Times are typical and max.

As a *very* rough rule of thumb you can get a single cycle through the
device in about 3 rise times or about 75 to 100 nS so it would probably
attempt to produce output with a 10 MHz square wave input. Maybe more I
would have thought. YMMV




        RM

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