A ring-oscillator-based on-chip sensor (OCS) includes a substrate having a semiconductor surface upon which the OCS is formed. The OCS includes an odd number of digital logic stages formed in and on the semiconductor surface including a first stage and a last stage each including at least one NOR gate including a first gate stack and/or a NAND gate including a second gate stack. A feedback connection is from an output of the last stage to an input of the first stage. At least one discharge path including at least a first p-channel metal-oxide semiconductor (PMOS) device is coupled between the first gate stack and a ground pad, and/or at least one charge path including at least a first n-channel metal-oxide semiconductor (NMOS) device is coupled between the second gate stack a power supply pad.