I am wondering how the maximum voltage ratings of Vce and Vcb work for BJT transistors.
Are they like MOSFETs in the way that the instant the maximum voltage is exceeded, they are damaged/destroyed? Or are they different in a way that there is some sort of pulse rating for them?
Best Answer
You may be thinking specifically about the VGS specification of a MOSFET. As soon as this is exceeded, the very thin gate oxide insulating layer is punctured and the transistor becomes useless.
There are other ways to destroy MOSFETs, too, that mainly involve causing them to dissipate excessive amounts of power in various ways. This is what the "safe operating area" diagram on the datasheet is all about.
BJTs do not have the delicate oxide layer, but they can still be destroyed by causing them to dissipate excessive amounts of power, by either melting the bonding wires or fusing the silicon itself and destroying the junctions.
For example, if you cause the transistor to conduct excessive amounts of current by exceeding its maximum VCE specification, the power dissipated (voltage × current) will be huge, leading to a rapid temperature rise that will destroy the device. But if you can limit either the voltage or the current to reasonable levels, such that the power remains within specification, you can often avoid permanent damage. In this way, BJTs are considered to be more "robust" than MOSFETs.