"Mr.T" MrT@home wrote in message
"Eeyore" wrote
in message ...
Is it a "conventional Class AB bipolar design" ?
It is class AB, and it is bipolar.
It's not conventional.
Brilliant wording on your part, since you get to decide
what is "conventional" it seems.
Anything other than a basic text book design is
non-conventional right?
Right now, the standard textbook design would be Doug Self's Blameless
amplifier design.
http://www.dself.dsl.pipex.com/ampins/dipa/dipa.htm
The distortion that Graham is talking about, Self calls "gm doubling"
distortion.
"It is not generally appreciated that moving into Class-AB, by increasing
the quiescent current, does NOT simply trade efficiency for linearity. If
the output power is above the level at which Class-A operation can be
sustained, THD increases as the bias advances into AB operation. This is due
to so-called "gm-doubling" (ie the voltage-gain increase caused by both
devices conducting simultaneously in the centre of the output-voltage range,
in the Class-A region) putting edges into the distortion residual that
generate high-order harmonics much as under-biasing does. This vital fact is
little known, presumably because gm-doubling distortion is at a relatively
low level and is obscured in most amplifiers by other distortions."