I have often had to measure and *prove* transistor batches to be fakes (in a way
that would convince the dealer to take the batch back).

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.

Peter


-- 
http://www.piclist.com PIC/SX FAQ & list archive
View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist