Composite amplifier in class A
I guess the only thing can be better than a good composite amplifier is good composite amplifier in class A.
From my experience one of the main sources of distortions in good composite amplifier, where output stage works in class B/AB, are signals induced in feedback path from supply rails. In this case supply rails will carry distorted (rectified) output current.
Of course, first of all you need to layout PCB carefully, trying to minimise those cross-talks. When all those measures are taken (at least I think so), and rather good level of distortion achieved (sub 0.1ppm for 1kHz), it is natural to try to move amplifier to class A.
Schematic shown below represents my vision of this device. Values, and schematic itself are not optimized yet. Output stage is quite a simplistic one, but at the same time this simplicity allows to use inclusive compensation up to quite high frequencies.
Bode plots show phase margin of the guy and total depth of negative feedback around output stage.
Will be interesting to hear if anyone has similar thought, and potential suggestion how to improve it.
Last edited by Shaq888; 5th May 2013 at 01:28 PM.