Hi all, I hope you guys can help me with my confusions here: 1) I don't understand the usage of transistors as switches. Why would you use transistors as switches, and how does that work?? 2) Why would you choose a PNP over an NPN transistor. I've been reading this book and I don't understand what this guy says. http://uploader.ws/upload/200707/bjt.jpg any help is greatly appreciated. thanks!