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How would one use NPN transistors only?

T

Terry Given

Jan 1, 1970
0
John Larkin said:
Then why does anybody use PNPs at all?

John

perhaps pnps with gold-plated leads provide a "purer" sound, especially if
hand assembled by one-legged lesbian dwarves :)

cheers
Terry
 
K

Ken Smith

Jan 1, 1970
0
How about specifying what is emittor and collector, and NPN and PNP?


NPN : make Vcc +
PNP : make Vcc -

Either way it works.
 
T

Terry Pinnell

Jan 1, 1970
0
Don't need transformer. But no one said what kind of amp. If you talking
audio amp, go to the library and look at old old late 60's issues of
"popular electronics" or "radio Electronics" or evne the british "wireless
world".

Or read the three recent (long) threads here (and in

alt.binaries.schematics.electronic):
Trouble shooting Push-Pull amp
Distortion from audio power amp
Are these 2N3055s borderline spec?

which include various examples.
 
J

Jan Panteltje

Jan 1, 1970
0
On a sunny day (Wed, 9 Jun 2004 02:54:36 +0000 (UTC)) it happened
NPN : make Vcc +
PNP : make Vcc -

Either way it works.
Yep, and you even added that nice boost cap from the output!
JP
 
J

Jan Panteltje

Jan 1, 1970
0
**** Post for FREE via your newsreader at post.usenet.com ****

On a sunny day (Wed, 9 Jun 2004 02:54:36 +0000 (UTC)) it happened
NPN : make Vcc +
PNP : make Vcc -

Either way it works.
Yep, and you even added that nice boost cap from the output!
JP
Sorry if this shows up twice, the usenet server teranews seems not working, posting via
post.usenet.com.
JP

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K

Ken Smith

Jan 1, 1970
0
[...]
Yep, and you even added that nice boost cap from the output!

The performance is really bad without the bootstrap.
 
J

Jim Thompson

Jan 1, 1970
0
All:

I am familiar with the typical amplifier using NPN, and PNP
transistors. It just makes good common sense, even to lay people like
me.

What about amplifiers that use ONLY NPN transistors? How would that
work? It may be elementary, but when I am trying to theorize that, it
just doesn't make sense to me.

There are a few people now building amplifiers with only NPN
transistors, and I understand the advantages, but I don't understand
how they make it work.

I will post the MC1554 amplifier to my website in a few minutes.

I won a coffee bet with Tom Frederiksen back in the mid 60's over this
scheme, proving I could make a power output stage with just NPNs.

...Jim Thompson
 
J

Jim Thompson

Jan 1, 1970
0
All:

I am familiar with the typical amplifier using NPN, and PNP
transistors. It just makes good common sense, even to lay people like
me.

What about amplifiers that use ONLY NPN transistors? How would that
work? It may be elementary, but when I am trying to theorize that, it
just doesn't make sense to me.

There are a few people now building amplifiers with only NPN
transistors, and I understand the advantages, but I don't understand
how they make it work.

See "MC1554-AudioPowerAmp.pdf" on the S.E.D/Schematics Page of my
website.

...Jim Thompson
 
J

Jim Thompson

Jan 1, 1970
0
All:

I am familiar with the typical amplifier using NPN, and PNP
transistors. It just makes good common sense, even to lay people like
me.

What about amplifiers that use ONLY NPN transistors? How would that
work? It may be elementary, but when I am trying to theorize that, it
just doesn't make sense to me.

See my other posts.
There are a few people now building amplifiers with only NPN
transistors, and I understand the advantages, but I don't understand
how they make it work.

There is NO advantage except *perhaps* cost. PNP-NPN combos to
emulate a power PNP are potentially unstable and are difficult to
match loop gain for positive and negative swing directions.

...Jim Thompson
 
R

Rick

Jan 1, 1970
0
Jim Thompson said:
See "MC1554-AudioPowerAmp.pdf" on the S.E.D/Schematics Page of my
website.


Don't see how this can work - the output stage's darlington has its
base and emitter clamped to almost the same voltage by the two
diodes connected to pin 8; it won't conduct.
 
J

Jim Thompson

Jan 1, 1970
0
Don't see how this can work - the output stage's darlington has its
base and emitter clamped to almost the same voltage by the two
diodes connected to pin 8; it won't conduct.

LOL! Do some more thinking before "shooting from hip" ;-)

...Jim Thompson
 
F

Fred Bloggs

Jan 1, 1970
0
Rick said:
Don't see how this can work - the output stage's darlington has its
base and emitter clamped to almost the same voltage by the two
diodes connected to pin 8; it won't conduct.

Well- that's the point- the pull-up Darlington is cut-off by the
conduction of the pull-down Darlington...the idea , for the output at
least, is borrowed from the earlier totem-pole output drive
architecture. The diode with anode to pull-up Darlington base is a
virtual reflection of the output node voltage to the base-node, ensuring
0V combined 2x Vbe drop, and therefore cut-off, whenever the diode at
pull-down Darlington collector conducts.
 
J

John Larkin

Jan 1, 1970
0
Don't see how this can work - the output stage's darlington has its
base and emitter clamped to almost the same voltage by the two
diodes connected to pin 8; it won't conduct.

I sure Jim will be dismayed to discover that hundreds of thousands of
these chips were manufactured, and none of them ever worked!

John


ps - two questions:

1) was this the first ocurrence of...


+----+---v+
| |
r |
| c
+---b
| e
| |
+-ka-+-----out
|
|
c
in--b
e
|
gnd


2) Did Jim Thompson invent crossover distortion?
 
J

Jim Thompson

Jan 1, 1970
0
I sure Jim will be dismayed to discover that hundreds of thousands of
these chips were manufactured, and none of them ever worked!

John


ps - two questions:

1) was this the first ocurrence of...


+----+---v+
| |
r |
| c
+---b
| e
| |
+-ka-+-----out
|
|
c
in--b
e
|
gnd

I don't know.

My extra diode cuts the deadband to a single vbe when a Darlington is
used.

I've used your representation to make TTL outputs from split supply
comparators with an extra diode to clamp the output to a "low" of
ground, as marked-up above. Note the R added in series with the
bottom collector....

+----+---o v+
| |
r |
| c
+---b
| e
| |
gnd-ak-+-ka-+----o out
|
R
|
c
in o--b
e
|
+---o v-
2) Did Jim Thompson invent crossover distortion?

No, but I've certainly created a lot ;-)

...Jim Thompson
 
R

Rick

Jan 1, 1970
0
Fred Bloggs said:
Well- that's the point- the pull-up Darlington is cut-off by the
conduction of the pull-down Darlington...the idea , for the output at
least, is borrowed from the earlier totem-pole output drive
architecture. The diode with anode to pull-up Darlington base is a
virtual reflection of the output node voltage to the base-node, ensuring
0V combined 2x Vbe drop, and therefore cut-off, whenever the diode at
pull-down Darlington collector conducts.

Thanks, Fred. Got it.
 
J

John Larkin

Jan 1, 1970
0
On Fri, 11 Jun 2004 10:59:35 -0700, John Larkin


I don't know.

My extra diode cuts the deadband to a single vbe when a Darlington is
used.

I've used your representation to make TTL outputs from split supply
comparators with an extra diode to clamp the output to a "low" of
ground, as marked-up above. Note the R added in series with the
bottom collector....

+----+---o v+
| |
r |
| c
+---b
| e
| |
gnd-ak-+-ka-+----o out
|
R
|
c
in o--b
e
|
+---o v-

We recently did a "pin driver" a lot like that, with surfmount
gaasfets instead of bipolars. Bottom transistor is a switched
constant-current gaasfet cascode. It works really good, 15 volt
programmable Vh/Vl swing and screaming fast, but it's a power hog.
Somebody needs to make a good IC pin/output driver.

John
 
J

Jim Thompson

Jan 1, 1970
0
We recently did a "pin driver" a lot like that, with surfmount
gaasfets instead of bipolars. Bottom transistor is a switched
constant-current gaasfet cascode. It works really good, 15 volt
programmable Vh/Vl swing and screaming fast, but it's a power hog.
Somebody needs to make a good IC pin/output driver.

John

MANY years ago I designed programmable pin-driver chips for GenRad.

...Jim Thompson
 
J

J M Noeding

Jan 1, 1970
0
Then why does anybody use PNPs at all?

John

In the early 60's PNP devices were more readily available and lower
cost than NPN devices, it was not difficult to build all sorts of
amplfiers, so it is just the other way around using NPN

Would have been nice trying PNP-type tubes.....
 
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