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November 29, 2010


Marty Kanner


I found your blog particularly interesting because some time ago, I set up a similar test to compare the size of transistor die between manufacturer's shipping transistors with the same part number. The test I ran was slightly different in that I discharged a capacitor with a fixed amount of energy into the collector-base and read the Vb-e on a scope immediatly after the discharge. By looking at the Vb-e rise as a temperature rise one could deduce that a lower rise was due to a larger thermal mass of the transistor structure.

At the time I compared mil-spec 2N2222's to commercial devices. I was shocked to find that the commercial transistors had a larger thermal mass and would therefore be more reliable.

John D.

Hi, Marty.

I would wonder though if the larger thermal mass of the commercial transistors might be reduced in future commercial devices in that a smaller die size would offer higher production yields. I once saw some photographs of the very earliest 2N3055 power transistor dies versus later ones and the size reduction looked substantial.

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