"Eeyore" wrote in
message
Arny Krueger wrote:

"Eeyore" wrote
Don Pearce wrote:
Eeyore wrote:

I'm concerned about the transconductance 'modulation'
with signal level since this introduces non-linearity.

Graham

That would be greatest in the transition region between
class A and class B.

Exactly spot-on Don and readily visible when looking at
a distortion analyser's output.

Agreed.

This is why Trevor's ideas baffle me.

The point that Trevor alludes to and Doug Self describes
in detail, is the fact that there are numerous other
sources of nonlinear distortion that can be bigger
problems in poorly designed amps.

If they're poorly designed !


Don't be proud Graham, go spend some time with Self's
article:

http://www.dself.dsl.pipex.com/ampins/dipa/dipa.htm

I've been there before Arny. There's nought Self can
teach me there.


My intention is to entirely eliminate this with a kind
of 'hybrid' output stage.

How? Other than class-A you'd need to come up with some
kind of Gm-halving circuit.

It is a 'form' of Class A that indeed meets the classic
definition but without the very high idle current. It
involves quite a radical rethink of the output stage.

In the past the usual approach to this has been to use a bias circuit that
keeps the output devices from ever turning fully off.