Class B Audio Power Amp

It's mostly in class B mode but it's slightlt in class A mode too. Nowadays it's hard to distinguish class B from class AB amps

Ah! Thanks man, so: how can I distinguish a class B from a class AB?

The quiescent current is what distinguishes them. Class B amps draw power from the supply only half a period. With class A amps the active device always draws power ( more or less). Class AB amps are designed so that at higher powers the amp works in Class B mode and at lower powers they work in class A mode. For instance your amp works in class B now. Check the current draw from the power supply. It cuts at half of the wave. The other part is handled by a decoupling output capacitor or in this case by the -12V power supply. Now decrease the input to 100mV and check the consumption again. You'll see that at lower power the current draw is more consistent. It doesn't get cut like before. That's where the class A part kicks in and the quality increases significantly. Class A amps usually are very inefficient. If you want 100W ypu have to dissipate another 200-300W in heat but at lower leves it's acceptable. On the other hand class B amps have inferior quality compared to class A amps but are more efficient so the heat losses are lower. Class AB is considered a good compromise between the quality offering of class A amps and the good efficiency of class B amps. I hope that clears it up a little ^^

Thank you for the great explanation, you cleared a lot! :)