Reverse bjt zener effect?

[throbscottle]

One of the things I have newly come across is connecting a transistor with open base, and emitter and collector connected the wrong way round (ie, for NPN, emitter would be at higher voltage than collector). Apparently the effect is the transistor breaks down in a zener like way.

Is there a particular use for this? Is it better to just use a zener? I ask because I saw it in a relaxation oscillator on the net, and thought, why not just use a zener?

Cheers

 

[audioguru]

The reverse-biased emitter-base of a silicon transistor has avalanche breakdown when the voltage is more than about 5V. Its maximum allowed voltage is listed on its datasheet.
Sometimes the forward-biased collector-base is in series.

But the emitter-base junction is small and has a low heat disssipation ability so it is slowly damaged by this "zener diode effect".
The damage causes the current gain of the transistor to become reduced.

 

[throbscottle]

Oh, right, thanks! Knowledge is power. I won't be abusing transistors this way then.