How are transistors able to amplify full AC signals? What I mean is that a transistor will conduct only if the base emitter junction is forward biased and when you apply high enough treshold voltage to turn it on. Like 0,6v. Then looking at the graph above, from 0 to 120 and from 120 to 0v the signal will be amplified perfectly. But what about when the polarity is reversed? How can transistors amplify that since they will be reverse biased?