Monitoring Proton Beam-induced Photodiode Degradation using Low-voltage Ring Oscillators

The influence of high energy Proton irradiation on the performance of Silicon photodiodes is investigated using two illuminated devices connected in series as power supply of a ring-oscillator realized with commercially available CMOS NAND gates and monitoring the output frequency. In order to consider the degradation of a single solar cell a 19-stage ring-oscillator fabricated in a standard CMOS process is operated. The circuit provides an integrated frequency divider and an output buffer, and stable voltage-to-frequency conversion is obtained for supply voltages provided by the photodiode down to 300mV.