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
John Larkin said:Then why does anybody use PNPs at all?
John
How about specifying what is emittor and collector, and NPN and PNP?
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".
Yep, and you even added that nice boost cap from the output!NPN : make Vcc +
PNP : make Vcc -
Either way it works.
Yep, and you even added that nice boost cap from the output!NPN : make Vcc +
PNP : make Vcc -
Either way it works.
[...]
Yep, and you even added that nice boost cap from the output!
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.
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.
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.
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.
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.
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?
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.
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
Then why does anybody use PNPs at all?
John