This is what I know about NPN BJTs (Bipolar Junction Transistors):

* The Base-Emitter current is amplified HFE times at Collector-Emitter, so that `Ice = Ibe * HFE`
* `Vbe` is the voltage between Base-Emitter, and, like any diode, is usually around 0,65V. I don't remember about `Vec`, though.
* If `Vbe` is lower than the minimum threshold, then the transistor is open and no current passes through any of its contacts. (okay, maybe a few µA of leak current, but that's not relevant)

But I still have some questions:

* How the transistor works when it is *saturated*?
* Is it possible to have the transistor in open state, under some condition other than having `Vbe` lower than the threshold?

In addition, feel free to point (in answers) any mistakes I made in this question.

Related question:

* [I don't care how a transistor works, how do I get one to work?](https://electronics.stackexchange.com/questions/5336/i-dont-care-how-a-transistor-works-how-do-i-get-one-to-work)