Crystal Vacuum Tube

Crystal Vacuum Tube

Buried deep within the circuitry of a Crystal Semiconductor analog-to-digital converter integrated circuit, we spotted this seemingly contradictory vacuum tube. In fact, the last stage of each channel in the converter has a power-ground capacitor shaped like a radio vacuum tube integrated into the design by engineer Greg Rohde. At the point in his career when this chip was designed, Greg was especially careful to disguise his silicon doodles because he had already felt the wrath of the Crystal chief executive officer. It seems that sometime earlier, there was a two-week delay in the tape out of a previous design while the initials of Greg and fellow designers were removed from the layout. The lesson here: hide your doodles well.


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