September 26, 2015

Diodes BC847BS - matched BJT pair : weekend die-shot

Diodes Incorporated BC847BS - pair of npn transistors with matched hFE. Internally it has 2 separate dies.
Die size 306x306 ┬Ám.

Second die:

Lithography repeatability is definitely better than this. Parameter matching is likely achieved by using adjacent dies from the wafer. 2 dies are used because one cannot place 2 BC847 transistors on the same die without significant changes to the technology (and it won't be BC847 anymore) - die bulk is transistor terminal.

Difference between the dies. Top metal is quite non-uniform optically (as usual) over the area, but this is unlikely to cause any electrical characteristics impact. Would be interesting to make similar difference photo for non-matched transistors.