High-voltage tolerant stimulation monitoring circuit in conventional CMOS process

Design techniques for realizing analog switch and rail-to-rail constant g_m opamp with approximately twice the standard supply voltages and signal swings are proposed in this paper. Based on these techniques, a 6 V stimulation monitoring circuit for monitoring 8 different stimulator outputs was implemented in a conventional 0.18 mum CMOS process using standard 3.3 V I/O devices. Maximum on-resistance for the switches was less than 3.15 kOmega and the variations on the opamp input g_m values were less than plusmn2.9% with a current consumption of 20 muA at 6 V.