The almost universal choice in semiconductor power amplifiers is for a unity gain output stage, and specifically a voltage follower. Output stages with gain are not unknown, 1 but they are not common.

The input stage of an amplifier performs the critical duty of subtracting the feedback signal from the input, to generate the error signal that drives the output. It ...

At one time, almost all electrical loads were linear — those that weren't made up such a small portion of the total that they had little effect on electrical system operation. That all changed, ...