Physical unclonable function cell and array

A method for operating a function cell system, the method comprising:

• supplying the same common AC voltage to a first FET device and a second FET device;
• detecting a transconductance factor (gm) of the first FET device in a first cell of the system and a gm of the second FET device in the first cell of the system;
• determining whether the gm of the first FET device is greater than the gm of the second FET device based on a comparison between a phase of outputs generated by the first and second FETS and a phase of the AC voltage;
• outputting a first voltage signal from the first cell of the system indicating that the gm of the first FET device is greater than the gm of the second FET device responsive to determining that gm of the first FET device is greater than the gm of the second FET device.

A method for operating a function cell system, the method comprising:

• providing power to the system;
• initiating a reading process comprising:
• selecting a first cell from a plurality of cells in the system;
• detecting and comparing a transconductance factor (gm) of a first FET device and a second FET device in the first cell;
• receiving a first bit value from the first cell indicative of the comparison of the gm of the first FET device and the second FET device of the first cell;
• storing the first bit value associated with the first cell;
• detecting and comparing a transconductance factor (gm) of a first FET device and a second FET device in the first cell, the detecting based on based on a comparison between a phase of outputs generated by the first and second FETS and a phase of the AC voltage;
• receiving a second bit value from the first cell indicative of the comparison of the gm of the first FET device and the second FET device of the first cell;
• determining whether the first bit value is the same as the second bit value;
• stressing a first FET device and a second FET device in the first cell if the first bit value is not the same as the second bit value;
• and
• outputting the first bit value responsive to determining that the first bit value is the same as the second bit value.