There is set forth herein a semiconductor structure including a plurality of test devices, the plurality of test devices including a first test device and a second test device. A semiconductor structure can also include a waveform generating circuit, the waveform generating circuit configured for application of a first stress signal waveform having a first duty cycle to the first test device, and a second stress signal waveform having a second duty cycle to the second test device. A semiconductor structure can include a selection circuit associated with each of the first test device and the second test device for switching between a stress cycle and a sensing cycle.