Topband: Any experience with 2N3553?

[Richard (Rick) Karlquist]

On 3/19/2020 10:04 AM, Don Kirk wrote:
> For grins and giggles I ordered 10 2N5109 parts on E-bay (from Asia).  Also
> ordered new ones from Mouser which I just received today, and also had one
> that I purchased a long time ago from Mouser (all of my  Mouser purchased

> Just FYI,
> Don (wd8dsb)
> _________________
I used the 2N3553 45 years ago as a medium power RF
amplifier, but not as a 2N5109 substitute.  I don't
know that it has the high and flat current gain and
the low base spreading resistance of the 2N5109 family.
That didn't matter for my application.

Remember that Motorola stopped making 2N5109's
in the year 2000.  Therefore any transistor with
a Motorola logo and a date code newer than 2000
is a prima fascia counterfeit.

I just received 20 each of the Central Semiconductor
2N5109's from Mouser.  If I were going to evaluate
transistors claiming to be 2N5109, I would want to check:

1.  DC current gain (beta), both the peak value
and the uniformity of beta vs collector current.

2.  f-sub-T

3.  Base spreading resistance.  This is determined
indirectly by measuring noise figure.

Depending on the application, one of more of these
could be important.

Rick N6RK