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

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Especially as the inverting gates have independent source and/or drain 
connections - series resistors can be used to lower even more the 
consumption when biased in the linear region...

On 6/28/2013 7:20 AM, Don Latham wrote:
> Maybe the old 4007 cmos would be better...
> Don
>
> paul swed
>> Yes it makes a very fine 35 Mhz oscillator and reasonably stable.
>> Been there and done that.
>> Hey the systems done. May remod it one day but bigger fish to fry with
>> the
>> d-psk-r
>> Regards
>> Paul
>> WB8TSL
>>
>>
>> On Thu, Jun 27, 2013 at 6:41 PM, David McGaw
>> <n1hac at alum.dartmouth.org>wrote:
>>
>>> Lower gain is better as long as it oscillates.  The 74HCU04 is
>>> unlikely to
>>> drive spurious responses.  The 74HC04 is OK as long as you keep the
>>> feedback gain low - sometimes a series resistor from the output to the
>>> resonant circuit is required.  A 74HC14 is the WRONG part for the job
>>> as it
>>> can and will oscillate without the crystal controlling it - just try
>>> it
>>> with a resistor for feedback and a capacitor to ground at the input,
>>> no
>>> crystal.
>>>
>>> David N1HAC
>>>
>>>
>>>
>>> On 6/27/13 6:30 PM, paul swed wrote:
>>>
>>>> I will say the fact is the 74hc14 is a bit of a power pig we are
>>>> talking
>>>> 12
>>>> ma. The rcvr is something much less like 100 ua. At least for the
>>>> moment
>>>> it
>>>> all works but 12 ma is a pig.
>>>> Especially when you take the signal out and knock it down to 100-200
>>>> uv.
>>>> Regards
>>>> Paul.
>>>>
>>>>
>>>> On Thu, Jun 27, 2013 at 5:37 PM, ed breya<eb at telight.com>  wrote:
>>>>
>>>>   Still having email problems - here we go again. This is second try,
>>>>> please
>>>>> excuse if both show up.
>>>>>
>>>>>
>>>>> 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
>>>>>
>>>>>
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