What is the VCEO Rating of a Transistor?

The VCEO Rating of a Transistor is the maximum allowable voltage that can be applied from the collector to the emitter of a transistor before it becomes damaged or destroyed.

The maximum allowable voltage that a junction of a transistor can withstand is called the breakdown voltage rating.

The VCEO rating which you see in a transistor datasheet is the breakdown voltage rating from the collector to the emitter of the transistor.

Applying a voltage from the collector to the emitter exceeding this rating can destroy the transistor. So make sure to check the datasheet for the transistor in use and design the circuit so that it receives a voltage lower than this rating.