Silicon-on-Insulator (SOI) technology has evolved from being exclusively devoted to “niche” market areas as radiation hard or high temperature applications to recently becoming a player in the high performance digital circuits market [IBM011, IBM012]. In addition, the international semiconductor community sees the fully-depleted (FD) variety, which is the one tested in this work, as one of the strong alternatives for solving the transistor scaling challenges in next generations of very deep sub micron processes [ITR01]. We will summarize here the characteristics of the type of SOI MOS devices used in this work, in order to compare later the performance of FD SOI and bulk CMOS analog blocks in low-voltage, micropower applications. This comparison is particularly focused on those blocks and performance aspects that are central to the proposed implementation of our study vehicle, the sense channel, as well as to the implementation of other pacemaker analog blocks. This is the case of the speed and precision of current mirrors, which are essential elements in the class AB stage proposed in Chapter 5, and of OTA characteristics such as the power-bandwidth trade-off, noise and offset.