US Patent 7868606 Process variation on-chip sensor

Improved process variation sensors and techniques are disclosed, wherein both global and local variations associated with transistors on an integrated circuit can be monitored. For example, respective circuits for sensing a global process variation, a local process variation between neighboring negative-channel type transistors, and a local process variation between neighboring positive-channel type transistors are disclosed. Further, in one example, a method for sensing a process variation associated with transistors on an integrated circuit includes providing at least one process variation sensor on the integrated circuit, the process variation sensor comprising a sensing portion including one or more transistors and a loading and amplification portion including one or more transistors, and operating the one or more transistors of the sensing portion and the one or more transistors of the loading and amplification portion in a subthreshold region of transistor operation such that when a threshold voltage of at least one of the transistors changes, a process variation is sensed.