This isn’t the hardest problem I’ve solved but I was damned proud of solving it when I did...
Was about to tape out a chip when we got a last minute change order... a 100kohm resistor needed to be added. This was an already laid-out, routed and optimized chip design that was ready to be fabbed.
A few hours later (including at least an hour of shouted obscenities) I found that I was able to snake through 100kohms of poly and diffusion resistor into our design without moving anything, violating any design rules or changing any operating points even after parasitic extraction.
Was about to tape out a chip when we got a last minute change order... a 100kohm resistor needed to be added. This was an already laid-out, routed and optimized chip design that was ready to be fabbed.
A few hours later (including at least an hour of shouted obscenities) I found that I was able to snake through 100kohms of poly and diffusion resistor into our design without moving anything, violating any design rules or changing any operating points even after parasitic extraction.