"Eeyore" wrote in message
...


Arfa Daily wrote:

I would suspect that breakdown voltage is a 'designed in' characteristic,
and will depend on physical dimensions of the transistor structure. The
"cherry picking" that the manufacturers do is usually related to gain and
gives something like an A, B or C suffix like BC108A or BC109B. How would
the manufacturer actually test a batch for breakdown voltage, as if you
take
the device to breakdown, then it is destroyed. Would the manufacturer be
prepared to stake the breakdown voltage of a production batch, on the
basis
of a few tested examples ? I'm not sure that he would. It's a bit like
having tested fuses really, isn't it ?

You're very mistaken.

The test is done with a current limited supply and the test is for a given
leakage current.

Due to necessity (the situation was forced on me) I've had both bipolar
and
mosfet devices selected very successfully for breakdown voltage.

By these guys in fact.
http://www.semelab.co.uk/

Graham


Ah, ok. I can see how that would work. Do manufacturers ( rather than
distributors like SEME) really still do this ? Seems like a lot of trouble
to go to. There are so many (hundreds of thousands ??) of transistor types
available now, I would have thought that it was possible to select one for
whatever breakdown voltages, gain, and whatever other parameters you might
require, without difficulty ? Maybe not. Thanks for the info.

Arfa