Design and characterization of a CMOS two-stage miller amplifier for ionizing radiation dosimetry

Abstract

The offset of a Miller amplifier is mainly due to an imperfect matching between its inputs. When the input transistors are MOSFETs, the exposure to ionizing radiation affect the threshold voltage of both transistors. With proper polarization, the shift in the threshold voltage impoverishes the matching in the input, increasing the offset. Hence, measuring the change in the offset during irradiation, one can estimate the absorbed radiation dose. In this work, a theoretical analysis is presented in order to establish the effect of ionizing radiation on the different blocks of the Miller amplifier. The design of a Miller amplifier and its fabrication on an integrated circuit for testing is described. The design and assembly of a dedicated hardware and software for data acquisition is also described. First results on the fabricated dosimeter in a 0.6μm commercial CMOS technology show a sensitivity of 60 mV/Gy and a resolution of 4 cGy.