"Rudge" wrote in message
o.uk...
I need a T039 NPN transistor with an 80 volt BVceo rating such as a BC142.

My nearest stockist holds the BC141 which has a BVceo rating of 60volt.

If I buy a BC141 and test the breakdown voltage, what are the chances that
it will exceed 80volt?



I would also like to know how manufacturers make these almost identical
transistors with different voltage ratings.



Do they just make a batch of BC140s and those which exceed 80v get stamped
'BC142'?



Or do they make separate production runs for each type?



Also, do the higher voltage versions loose out on some other parameter
such
as gain?



Many thanks,

Rudge



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 ?

Arfa