Suppose the following audio amplifier configuration:
Suppose that Vc is correctly configured to be in the middle of the rail. So, at rest, Vc = 4.5V, Ve = 0 and Vb = 0,6V, right?
Suppose I inject a 1Vpp audio signal at the base.
As the signal rises from 0 to 0.5V, Vb increases from 0.6 to 1.1V. Because Vbe > 0.6V, the transistor will conduct. Ic will increase. As Ic increases the voltage drop on R1 increases, forcing Vc down. So, we see that Vc and Vb are 180 degrees out of phase.
What I do not understand is how will this occur on the negative cycle of the audio.
As the audio starts going from 0 to -0.5V, Vb will reduce from 0.6 to 0.1. Because Vbe will be less than 0.6 the transistor will cut off. No current will flow from collector to emitter.
In my mind, as the transistor cuts off, Vc will be 9V but this circuit is mentioned on the web as being an amplifier. It seem to me more like a half cycle rectifier...
What am I missing?