The design of a sensing channel for implantable cardiac pacemakers in CMOS on silicon-on-insulator (SOI) technology is presented. The total current consumption is lowered to only 110nA thanks to the optimization at the architectural level, the application of a new class AB design approach at the operational transconductance amplifier (OTA) and the exploitation of the improved characteristics of thin-film fully depleted SOI CMOS technology. The core of the prototyped sense channel (OTA and comparator) occupies 0.06mm/sup 2/ in a 3/spl mu/m technology and is suitable for operation from implantable grade batteries with power supply voltages from 2.8V down to 2V. Experimental results of the building blocks and complete sensing channel performance are presented. The achieved results demonstrate the benefits of fully depleted SOI CMOS technology for micropower applications.