Total dose effects on operational amplifiers with MOSFET input

In this paper, we explore the total ionizing dose effects on the offset voltage of the commercial off-the-shelf high-voltage MOSFET-input operational amplifier CA3140 for use in dosimetry applications. The devices were irradiated under different biasing conditions using a 60Co γ-ray source from a radiotherapy unit. Both experimental results and a physics-based analytical model show that the radiation response of the operational amplifier is governed by the radiation-induced degradation of the MOSFET input pair. Estimates from measurements give a sensitivity of 2.5 mV/cGy(SiO2) and a noise equivalent dose of 0.9 cGy(SiO2).