# What is "Collector-Emitter Sustaining Voltage”

In many transistor datasheets, there is a $V_{CEO(sus)}$ specification, what's the meaning of it? Can someone give some explanation or a link is just OK.

This document entitled "Electrical Ratings and Characteristics of Power Semiconductor Switching Devices" contains probably the best picture of this fairly obscure-to-most-engineers phenomena: -

Basically it's to do the the collector emitter breakdown voltage with the base open circuit (it's most vulnerable). The graph above shows 5 scenarios of the base bias ranging from open circuit to heavily reverse biased. Any BJT will behave like this. Note the red box along the voltage axis is the value of $V_{CEO(SUS)}$. It's also known as V(BR)ceo in other data sheets or BVceo in the graph below: -

• That's a [chapter of a] free book by the way: homepages.eee.strath.ac.uk/~bwwilliams/book.htm – Fizz Nov 2 '15 at 21:01
• And the middle schematic there featured in a fairly recent question (as you probably know): electronics.stackexchange.com/questions/193603/… – Fizz Nov 2 '15 at 21:18
• @RespawnedFluff good find on the 1st comment but I didn't follow your 2nd comment. What middle schematic and why would I recognize that question from this one? – Andy aka Nov 2 '15 at 21:23
• The improvised use of a transistor [as a zener] with its base connected to its emitter was the topic of that other question and is also shown in the middle schematic of your first figure here (Vces). The reason for that connection [in the other question] was to maximize the breakdown voltage; well, maximize it in a cheap way; it seems one can do better with some DC biasing inserted there. – Fizz Nov 2 '15 at 21:28
• @RespawnedFluff oh yeah how freaking dumb am I sometimes LOL – Andy aka Nov 2 '15 at 22:22

Is the breakdown voltage, take exemple the MD2001Fx datasheet, if you see Figure 2 what they calling the collector-emitter sustaining voltage (700V) is the collector-emitter breakdown voltage.
This is a definition for what they call Collector-Emitter sustaining voltage.