[time-nuts] TAPR TICC boxed (input protection)

Tim Shoppa tshoppa at gmail.com
Tue Apr 11 08:22:14 EDT 2017


I have a really naive question: how can picoamp leakage parts be relevant in low impedance input pulse conditioning to an interval counter?

Tim N3QE

> On Apr 11, 2017, at 7:46 AM, Bob kb8tq <kb8tq at n1k.org> wrote:
> 
> Hi
> 
> 
>> On Apr 11, 2017, at 7:05 AM, Charles Steinmetz <csteinmetz at yandex.com> wrote:
>> 
>> David wrote:
>> 
>>> I ended up qualifying 2N3904s based on manufacturer and lot and I
>>> think we ended up using ones from Motorola.  I wish detailed process
>>> information like National had was available from every manufacturer.
>> 
>> It is, if you ask the process engineers for it.  (From the Big Boys, that is.  These days it seems discrete devices are being fabbed by dozens of "garage" operations.  I can't speak for them, and wouldn't think of buying product from them.)
> 
> If you dig into where your simple discrete part was made, you might be surprised. That’s even true of outfits you would
> consider to be a “Big Guy” from days gone by. The real answer to selection today is to buy the automotive part.
> That’s about the only thing anymore that locks down the sourcing, testing, and the process. If you buy a “normal” part,
> it might have been made anywhere by just about any process. Yes, that’s scary and it raises a lot of questions. It is
> a change that has happened over the last decade or two without a lot of publicity. 
> 
> Bob
> 
> 
>> 
>> Best regards,
>> 
>> Charles
>> 
>> 
>> 
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