[time-nuts] wwvb 60 khz tuning fork crystals Some insights

[paul swed]

I suspect the threads been hijacked into a why doesn't email work.
I would say lets kill this thread.
Regards
Paul
WB8TSL


On Thu, Jun 27, 2013 at 5:35 PM, ed breya <eb at telight.com> wrote:

> Hal Murray said:
> >They make 74xU04 for many values of x.  The U is for Unbuffered.  They
> have
> lower gain in the linear region.
> I thought they were intended to be used for things like this, but I don't
> understand that area.  Can anybody give me a quick lesson or point me at a
> good URL?<
>
>
> I always thought the unbuffered "U" versions were preferred for ring
> oscillators mostly to save power - you don't want the high-drive output
> stages to be cooking away in linear mode if not needed. The propagation
> delay can also be less since the U ones have only one stage instead of
> three (the building block is the totem-pole inverter stage), but they can't
> drive very much load anyway. I think that most MSI and LSI parts that have
> built-in ring/crystal oscillator sections use the U topology, but I don't
> think there's anything special about it - it's the simplest thing that
> works.
>
> I've made quite a few CD4000 and 74HC oscillators, and never worried too
> much about U versions or not, except for battery-run items where power is
> critical (or you can run the oscillator at lower voltage). Often they are
> made from inverting gates that are part of a shared package, where you
> wouldn't want puny drive capability in the other gates anyway. They are
> relative power hogs though, whenever linear biasing is needed. Except in
> the 4000 series, I don't know if U versions are available in anything but
> the '04 hex inverter, but I suppose it's possible. I think the
> Schmitt-trigger types like HC14 are necessarily buffered, so have three
> stages, since you need a non-inverted version of the signal for the
> positive feedback to the input.
>
> I've never tried making one in 74AC - I don't know if it's even possible
> to bias one up that way without it burning up. I'm working on some related
> circuits now, so maybe I'll set up an experiment to see how much current it
> would take for one inverter - I've often wondered about this.
>
> I read about this years ago in various CMOS application notes, so I may be
> missing some key points - there should be plenty of info online. The older
> generation (when CMOS was fairly new) info may provide more detail about
> the guts than that related to the newer, higher performance families.
>
> Ed
>
> ______________________________**_________________
> time-nuts mailing list -- time-nuts at febo.com
> To unsubscribe, go to https://www.febo.com/cgi-bin/**
> mailman/listinfo/time-nuts<https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts>
> and follow the instructions there.
>