"Roy Lewallen" wrote in message
...
Connect it exactly the same as you would an NPN, but reverse the
polarity of the power supply voltage. If there's a bias circuit using a
diode, the diode (and bias supply polarity, if it's a separate supply)
should also be reversed.

If it's necessary for you to use the PNP with a positive supply voltage,
it's still possible, but it complicates the circuit, and adequate
bypassing becomes essential and sometimes difficult. In that case, a
diagram (and preferably a layout) of a known working circuit is desirable.

All other things being equal, a PNP generally has lower ft and higher
capacitance than an NPN, which is probably why they're less commonly
used. This difference is due to the basic physics of the device (lower
mobility of the carriers, as I recall).

Roy Lewallen, W7EL



I always wondered why Motorola (of all peopled) used PNP RF
transistors in the final and two driver stages in their Micor base
station and mobile radios.

Pete

Uncle Peter wrote:

I always wondered why Motorola (of all peopled) used PNP RF
transistors in the final and two driver stages in their Micor base
station and mobile radios.


Were those perhaps germanium transistors? The first Ge transistors were
PNP, and the first (Ge) audio power transistors I recall seeing in wide
use, in auto radios, were PNP. I'm not sure why PNP was favored in the
early days, whether due to some basic physics reason or some more
practical processing or production considerations.

Roy Lewallen, W7EL

Roy Lewallen wrote:
I'm not sure why PNP was favored in the
early days, whether due to some basic physics reason or some more
practical processing or production considerations.

I always had the distinct impression it was processing/production
considerations.

--
Frank Abagnale on "Rathergate" (the CBS forgery scandal):
"If my forgeries looked as bad as the CBS documents, [the movie "Catch Me If
You Can"] would have been 'Catch Me In Two Days'."

"Roy Lewallen" wrote in message
...
Uncle Peter wrote:

I always wondered why Motorola (of all peopled) used PNP RF
transistors in the final and two driver stages in their Micor base
station and mobile radios.


Were those perhaps germanium transistors? The first Ge transistors were
PNP, and the first (Ge) audio power transistors I recall seeing in wide
use, in auto radios, were PNP. I'm not sure why PNP was favored in the
early days, whether due to some basic physics reason or some more
practical processing or production considerations.

Roy Lewallen, W7EL

Hello Roy

These fairly modern devices, with 211-xx style flange mounts. Although
they were marked with Motorola Communications inhouse numbers,
they appear to have been part of the general Motorola RF transistor
family, with complimentary NPN equivalents.

pete

Hm, y'got me, then.

Maybe they had a big stock of them left over from a canceled project, so
decreed that the engineer had to design them in so they'd get used up.

That sort of thing does happen. . .

Roy Lewallen, W7EL

Uncle Peter wrote:

Hello Roy

These fairly modern devices, with 211-xx style flange mounts. Although
they were marked with Motorola Communications inhouse numbers,
they appear to have been part of the general Motorola RF transistor
family, with complimentary NPN equivalents.

pete