njackiw:
Understood. Per my subject, I am building "a simple 8-ohm speaker amp" at novice level driven by an arduino and a 5v powersupply.. nothing HiFi or high powered!
Now, when you say, "driven by an Arduino", do you mean from a digital output -- i.e. using something like the tone() function?
If so, then all you need is a square wave amp. Like this:
R2 is the Volume Control.
But, I get it. You want to get an audio power amp working. 