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In a message dated 10/30/2016 6:07:56 P.M. Eastern Daylight Time,  
davidwhess at gmail.com writes:

That is  always the danger when using parts for characteristics not
guaranteed in  the specifications.
YES



Sometimes a process just becomes obsolete necessitation new  parts to
be fabricated on a new process.  Or a process may have  enough
variation that some lots or parts meet unguaranteed specifications  and
others do not.  Occasionally a minor update is made to correct  a
problem or improve yield that significantly changes  unguaranteed
specifications.
 This was not the case with Infinion. They moved the production from  
Germany to Austria and did change the process....



And of course the company could be bought resulting in the  process or
parts you are relying on being  discontinued. 

That is the reason why I / we will design or own transistors as other also  
do. There is a possibility that some oscillator producers will get into 
trouble  .. This can happen with the crystals too 

 I am currently worrying
about this with Linear Technology  being bought by Analog Devices and
NXP being bought by Qualcomm.  In  the case of Qualcomm, I cannot see
them being in the discrete parts  business.

As far as testing, nobody likes to test for noise or low  leakage for
that matter.  Test time costs money and low frequency  noise testing
especially takes a lot of time.  The example I like to  use for this is
the LMC6081 ($0.83) and LMC6001 ($5.76) operational  amplifiers; the
later is identical to the former except it spends a lot  more time on
the tester to guarantee its lower input bias current.   Common small
signal transistors are usually specified with 50 or 100  nanoamps of
leakage even though it is often 1000s of times lower because  that is
as good as the automatic testers can do  quickly.

 
I use special  set of test oscillators at different  frequencies  with 
rivets to connect the transistors. Before I forget  this, the same is valid for 
diodes getting noisier. I have arranged to have a  custom diode developed 
for us, in a foundry,   Important point !
 
The R&S FSWP signal analyzer takes only  few seconds to  test  all 



On Sun, 30 Oct 2016 17:06:52 -0400, you wrote:

>It has  to do with the manufacturing process and a reduction in cost. I 
can   
>not speak for other companies, Infinion "killed" the good phase  noise   
>performance but the large signal noise is not  specified in the data sheet 
so  
>they are legally   "clean"
> 
>>In a message dated 10/30/2016 4:56:38 P.M. Eastern  Daylight Time,  
>>davidwhess at gmail.com  writes:
>>
>>You  mentioned suitable transistor  availablity being an increasing
>>problem and I  have run across  that myself.  Do you expect Qualcomm's
>>aquisition of  NXP  to have an impact?
>>
>>NXP is currently the best source I  have for fast  complementary pairs
>>or even just fast  PNPs.
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