Structures and methods for deriving stable physical unclonable functions from semiconductor devices

A semiconductor device including circuitry configured to derive a physical unclonable function, the circuitry comprising:

• a plurality of bitcells, wherein:
• each bitcell in the plurality of bitcells comprises a differential transistor pair including a plurality, fewer than three, of transistors,
• each bitcell outputs a ‘1’ value when a threshold voltage of a first transistor in the plurality of transistors exceeds a threshold voltage of a second transistor in the plurality of transistors, and
• each bitcell outputs a ‘0’ value when the threshold voltage of the second transistor exceeds the threshold voltage of the first transistor;
• and
• sense amplifier circuitry configurable to read values from the plurality of bitcells, the sense amplifier circuitry comprising:
• differential sense amplifier circuitry having a current stage and a voltage stage, the current stage having a first leg coupled to a bit line of the first transistor and a second leg coupled to a bit line of the second transistor, the voltage stage comprising a comparator coupled between the first leg and the second leg, and
• margin circuitry configurable (i) to selectably bias reading of the plurality of bitcells toward one of ‘0’ values and ‘1’ values by a current generator coupled to a respective one of the first leg and the second leg, and configured to selectably inject at any one time a margining current into at most one of the first leg and the second leg, (ii) to identify addresses of bitcells having a stable ‘1’ value when the margin circuitry is configured to bias reading of the plurality of bitcells toward ‘0’ values, and (iii) to identify addresses of bitcells having a stable ‘0’ value when the margin circuitry is configured to bias reading of the plurality of bitcells toward ‘1’ values.