Collector - emitter breakdown voltage of BJT

[chikenlover]

Hello everyone!

Simple question - does the collector emitter breakdown voltage actually decreases with increased collector current? Or is it just the dissipated power that burns the transistor ?

[Simon]

I think your confusing max voltage (breakdown) with Vce during operation.

Breakdown voltage usually refers to the maximum voltage you can apply to the transistor before it is damaged. This mostly applies to when it is off as when it is on the voltage drop is low and any applied voltage will fall on the load mostly unless the transistor is part on. Think of it as a mechanical switch. If you apply a voltage to it when it's open through a load the full voltage falls across the switch and it needs to be rated for it. Once closed it's just a conductor so low resistance and all of the voltage falls to the load.

[Alexei.Polkhanov]

By collector current do you mean reverse saturation current? I think with increase of temperature reverse breakdown voltage will be going up to and with it reverse saturation current will also go up. At least this is how it is for diodes in reverse. For avalanche diodes and zener diodes this behavior is different - see this link for example: http://conceptselectronics.com/diodes/effect-temperature-diode-characteristics/. So I am guessing collector-emitter breakdown will be more like avalanche breakdown.