> Speed is usually not an issue, what they do is skimp on die size (smaller
> generic dies are faster) and on bonding (thermal and electrical). So there are 3
> tests: Vcesat at reasonable beta, sustained power dissipation (mount on heatsink
> and bias to burn power to spec), and fast pulse test (50R collector resistor,
> drive with pulse geneator and look at slope with scope). Sometimes voltage is
> also an issue, test for leakage at Vceo using the circuit with the heatsink from
> above.

That's the kind of detailed advice I hoped for! In my case it is 
MJ15003/4 transistors, so there is quite some heat, current, voltage 
involved (more than my bench supplies can provide). I'll try for the 
Vcesat at the highest current I can manage, that seems the easiest one.

-- 

Wouter van Ooijen

-- -------------------------------------------
Van Ooijen Technische Informatica: www.voti.nl
consultancy, development, PICmicro products
docent Hogeschool van Utrecht: www.voti.nl/hvu

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