Please, explain the process of breakdown; how exactly this protective diode protects the transistor?
In a Horowitz & Hill book, "The Art of Electronics", 2nd edition, in "Chapter 2 - Transistors" (page 68), i read the following:
- Always remember that the base-emitter reverse breakdown voltage for silicon transistors is small, quite often as little as 6 volts. Input swings large enough to take the transistor out of conduction can easily result in breakdown (with consequent degradation of hFE unless a protective diode is added (Fig. 2.10).
Can't figure out how this diode protects the transistor from breakdown if the current goes only in one direction in this diode.