On Sat, 02 Apr 2005 13:09:58 -0500, Ken Scharf
wrote:

K7ITM wrote:
Jan-Martin wrote, "perhaps not so much for RF, but I wonder why you
don't see NPN/PNP combination for darlington transistors - with Vbe =
0.55-0.6V"

Actually, I think if you look at schematics of transistorized audio
amplifiers, you'll find examples of about every practical combination
of two and three transistors, used to build complimentary output
stages. If I understand correctly what you are suggesting, I'm quite
sure I've seen that configuration. In the 1960's and into the '70's,
there were a lot of games played to try to pair up NPN power
transistors with PNP drivers to get PNP-equivalents and NPN-equivalents
that were as nearly symmetrical as possible while giving high current
gain, since PNP power transistors weren't up to performing as well as
the NPNs in that era.

Cheers,
Tom

You can cascade NPN-PNP transistors by connecting the collector of
on transistor to the base of another (of different polarity). I recall
a circuit that used two pnp and one npn transistors in a three way
cascade, the final transistor was a PNP power type (all Ge).
It used 2n107, 2n170, and 2n301 transistors as a simple audio
amplifier for a phonograph.

I suggested this configuration in my poster a fortnight ago, apart
from that I wouldn't use a germanium power transistor, or better
wouldn't use germanium transistors at all


---
J. M. Noeding, LA8AK, N-4623 Kristiansand
http://home.online.no/~la8ak/91n.htm

J M Noeding wrote:
On Sat, 02 Apr 2005 13:09:58 -0500, Ken Scharf
wrote:


K7ITM wrote:

Jan-Martin wrote, "perhaps not so much for RF, but I wonder why you
don't see NPN/PNP combination for darlington transistors - with Vbe =
0.55-0.6V"

Actually, I think if you look at schematics of transistorized audio
amplifiers, you'll find examples of about every practical combination
of two and three transistors, used to build complimentary output
stages. If I understand correctly what you are suggesting, I'm quite
sure I've seen that configuration. In the 1960's and into the '70's,
there were a lot of games played to try to pair up NPN power
transistors with PNP drivers to get PNP-equivalents and NPN-equivalents
that were as nearly symmetrical as possible while giving high current
gain, since PNP power transistors weren't up to performing as well as
the NPNs in that era.

Cheers,
Tom


You can cascade NPN-PNP transistors by connecting the collector of
on transistor to the base of another (of different polarity). I recall
a circuit that used two pnp and one npn transistors in a three way
cascade, the final transistor was a PNP power type (all Ge).
It used 2n107, 2n170, and 2n301 transistors as a simple audio
amplifier for a phonograph.


I suggested this configuration in my poster a fortnight ago, apart
from that I wouldn't use a germanium power transistor, or better
wouldn't use germanium transistors at all
Well not today, but in 1965?
Look at the part numbers I gave! Ancient History!

On Sat, 02 Apr 2005 17:31:35 -0500, Ken Scharf
wrote:

J M Noeding wrote:
On Sat, 02 Apr 2005 13:09:58 -0500, Ken Scharf
wrote:


K7ITM wrote:

Jan-Martin wrote, "perhaps not so much for RF, but I wonder why you
don't see NPN/PNP combination for darlington transistors - with Vbe =
0.55-0.6V"

Actually, I think if you look at schematics of transistorized audio
amplifiers, you'll find examples of about every practical combination
of two and three transistors, used to build complimentary output
stages. If I understand correctly what you are suggesting, I'm quite
sure I've seen that configuration. In the 1960's and into the '70's,
there were a lot of games played to try to pair up NPN power
transistors with PNP drivers to get PNP-equivalents and NPN-equivalents
that were as nearly symmetrical as possible while giving high current
gain, since PNP power transistors weren't up to performing as well as
the NPNs in that era.

Cheers,
Tom


You can cascade NPN-PNP transistors by connecting the collector of
on transistor to the base of another (of different polarity). I recall
a circuit that used two pnp and one npn transistors in a three way
cascade, the final transistor was a PNP power type (all Ge).
It used 2n107, 2n170, and 2n301 transistors as a simple audio
amplifier for a phonograph.


I suggested this configuration in my poster a fortnight ago, apart
from that I wouldn't use a germanium power transistor, or better
wouldn't use germanium transistors at all
Well not today, but in 1965?
Look at the part numbers I gave! Ancient History!

I believed the discussion was really about RF transistor application,
but talking about those toxic transistors, is there any known cases
where persons have deceased after opening a power transistor?


---
J. M. Noeding, LA8AK, N-4623 Kristiansand
http://home.online.no/~la8ak/91n.htm