bjt max Vce question

[wakoko79]

hi, I'm just wondering, mmbt3904 listed its Vce(max)=40V

What if I wire it like shown in the picture?
If the npn is cut-off, the voltage Vce=60V, since Ir7=0V

would this destroy the bjt? or if not, will the lifespan or performance be affected? or is the Vce(max) rating is only when the bjt is operating(i.e. linear/saturation)?

Thanks!!!

 

[ericgibbs]

hi,
Depending upon the connection of the Base circuit, it will most likely go to into avalanche mode.

This should not damage the transistor providing the IC is approx 60mA.

Transistors are often used in avalanche mode to produce very fast switching times, eg: laser diode driving.

EDIT:
Found a circuit for the 3904 showing this effect.

**broken link removed**

 

[crutschow]

In general you never want to apply more collector-emitter voltage than the Vce(max) rating of the transistor. Not all transistors will tolerate an avalanche condition without deterioration or failure.