Interesting BiCMOS circuits in the Pentium, reverse-engineered

Ah, memories. I was a manufacturing engineer in a bipolar factory from 1989 to 1992, and BiCMOS was the perennial hope for a future for our acquired skills. When word broke that the Pentium would have one, it seemed significant. On the whole, though, it didn't have the impact that was hoped for; bipolar hangs on (like COBOL) in certain niches, but I think despite the theoretical advantages, the disadvantages of having to think about both bipolar and CMOS transistors in the engineering, was too much of a price to pay.

Lesser known reasons: as bipolar transistors went to polysilicon gates (which have a tiny, ~1-2 Angstrom thick layer of oxide in them) and MOS transistors started to become leakier through their ever-shrinking gate oxides, the distinction between MOS and bipolar transistors became fuzzier. Modern MOS transistors leak less current through their gate oxides than the bipolar transistors did through the polysilicon emitter, but the physics of the two is not as different as it was twenty years ago.

Is BiCMOS radical woke? :-) Author here for your Premium questions...