strange defect with MMBT2222

[Spehro Pefhany]

NO.

The 2N2222 is a TO-18 part. The whole point of a JEDEC spec is that it's a
*standard*. It doesn't change willy nilly.



NO.

The *PN*2222 is TO-92.

Graham

Or maybe P2N2222A.

http://www.onsemi.com/pub/Collateral/P2N2222A-D.PDF

Best regards,
Spehro Pefhany

 

[Michael A. Terrell]

Yes, I agree, high-freq RF oscillation. I'd lay the blame
to the simple wiring of Jamie's test fixture, which should
have one or two judiciously-placed ferrite beads. He gets
a transistor with slightly higher fT and lower capacitance,
which is normally considered a better transistor, and calls
it defective. I see he tells us Fairchild is replacing the
defective shipment. It's good when a supplier jumps to say
the customer is right, but sometimes they may be wrong.

They might still have the same problem with the new shipment, if it
was casued by a slight improvment in the production process and their
design is marginal. Using old samples only show that the design 'used
to work'.


--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
Member of DAV #85.

Michael A. Terrell
Central Florida

 

[Jim Thompson]

They might still have the same problem with the new shipment, if it
was casued by a slight improvment in the production process and their
design is marginal. Using old samples only show that the design 'used
to work'.

Likely. The real problem is lack of uniformity as to what an MMBT2222
really is. Everything that matches the DC characteristic is labeled
MMBT2222, no matter what the fT.

...Jim Thompson

 

[Michael A. Terrell]

Likely. The real problem is lack of uniformity as to what an MMBT2222
really is. Everything that matches the DC characteristic is labeled
MMBT2222, no matter what the fT.

That was one of the reasons our 'Item Masters' stated what BRAND was
acceptable for 99% of our inventory. In a few cases we had the same
generic part number with different stock numbers for different
products. The company was known for designing circuits with available
parts to do the job. Their early designs had way too many 'S.I.T.'
components for my taste, but it was the only way to build them, at the
time.


Even passives that have the same specs can give you fits, at times.


--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
Member of DAV #85.

Michael A. Terrell
Central Florida

 

[Tom Bruhns]

We use lots of MMBT2222's, and I haven't seen any notes about
strangenesses in them; not sure if Fairchild is an approved vendor for
us for that particular part though.

Turns out they are, along with _several_ others (with variations on
the prefix letters).

Since the MMBT2222 data sheets I have don't specify a maximum ft, I
assume it's up to me to apply them in a way that they have a
reasonable chance at stability. I haven't had much trouble with that,
but suppose that one day I'll be bit by it. I have been bit by
oscillations in other parts (op amps; inputs to high speed ADCs...)
enough that I know some of the symptoms. And I'd expect that since
the '2222 has some other specs it must meet, the ft isn't going to go
too crazy high on me. Seems like for garden-variety small signal
transistors, it's the unusual one that DOES spec a max ft -- counter-
examples could prove me wrong, and I'd be happy to know about them.

Cheers,
Tom