This isn't a homework problem, but I guess it is similar to one. I'm looking at the circuit from http://www.electroboom.com/, the latest post. I also included the circuit in the pdf attached. I want to know how this circuit works by calculating values in the circuit. This circuit is a power amplifier where Vin is an audio signal from a mp3 player. My work is found in the same attachment. I'm not sure if I calculated the modes of operations correctly for the transistors but I think they look about right. Besides the question if my work is correct, here are my other questions 1. How do I calculate the current going through the NPN_CE and PNP_EC junction when they're not in cutoff? 2. How do I calculate the current or the power going into the speaker assuming its something like an 8ohm speaker? 3. Is Vbe_on for transistors always 0.7V? I'm not sure how to read the parameters on the datasheets. I didn't see 0.7V anywhere. I just assumed it was 0.7V since the blog from http://www.electroboom.com/ said so. I'm having a lot of trouble understanding datasheets.