The unique requirements of biomedical electronics develop from its electrical interface with living tissue, which may involve cutaneous electrodes for an external instrument or wearable device or subcutaneous electrodes in implantable devices as well as other sensors and electrical or mechanical actuators. The overarching requirement for safety and reliability demands designs that include electrical isolation, fault tolerance, and tightly controlled outputs. Additional requirements include small size and low weight without reduced longevity. These needs are normally addressed by using the latest low-power technology with high-power density batteries. Integration of electronic devices into medical systems requires fast, reliable, low-power communication between medical devices and a base station or between multiple implanted or wearable medical devices. Strategies to meet these requirements with low-voltage CMOS integrated circuit techniques and micropower circuit and system design are developed in this chapter.