2 Mar
2006
2 Mar
'06
12:25 p.m.
Fons said:
On Thu, Mar 02, 2006 at 03:04:29PM +0900,
res0u2uc(a)verizon.net wrote:
Sorry -- I have to split a hair here. You're describing Class AB.
Class A means that you are never out of the linear region of conductance
for the semiconductor. This means that there are no "halves" to an output
stage.
Hmm. Well, my knowledge here isn't great, but
I think having
a capacitor at the output of a Class A amplifier would
prevent it from operating with a DC offset.
No. The essential point of (balanced) Class A is that both
halves of the output stage (the one giving the + and
the one giving the - voltage) are both active all the
time and never 'cut off'. Anyway the DC component required for Class A would
burn
your speakers in a fraction of a second.
Only if you run from 0 to Vmax with a positive DC bias. You can run a
class A device between positive and negative rails so that the output has
no DC offset.
There's no free lunch, though -- you want to consider a lot of practical
things that outweigh the "pure" approach -- boy, your devices had better
be thermally stable, class A is pretty wimpy for power dissipation, what
happens to your DC offset when your output device fails, and a lot more
that have little to do with Linux, so I'll stop there...
Upshot: It's easier to make class A preamps than power amps.
("Man! I can't believe you got me monologuing again!")
--The Incredibles
Cheers,
Phil M
--
Dept. of Mathematics, 342 Machray Hall
U. of Manitoba, Winnipeg, Manitoba, Canada R3T 2N2
Office: 446 Machray Hall, 204-474-6470
http://www.rephil.org/ phil at rephil dot org