I take next sample schematic.
This is only an output stage of any real power amplifier. It's clear when it's work in B-class the every BJT amplify only one half of input signal. But what it means if it works in class A. I know that the current always go through BJT if it works in class A. And if signal is too small but enough to open the BJT it will amplify both negative and positive signal swings before the signal level achieves some value above that only part of that signal will be amplified with "N" or "P" stage accordigly. Ok, if both parts of small signal amplified with every parts of a power amplifier, how do they added on load resistance? They both must have opposite direction and must differ from each other and the 0 must be on load. Here is a trick that I can't understand. Any suggestions?