Hello, For a school project I need to build a simple but working speaker. I am currently stuck on explaining how the signal amplifier works. Here is a schematic of an AB amplifier from Wikipedia. I have add a positive and negative sign indicating the connection of the battery. It contains 2 transistors, an NPN and PNP. These react individually on the polarity of the input signal (AC). The amplified semi waves then combine and form an audiosignal. I can only confirm that it works when the input signal is positive, then the PNP transistor blocks the current and all the current flows through the speaker. If its negative then the NPN transistor completely blocks the DC power supply. Could you guys please explain how the rest works, would be really grateful.