The book provides in-depth explanation of circuit design for wireless, implantable Systems-on-Chip (SoC) for body sensor networks. The authors describe a closed-loop implantable micro-stimulator SoC, capable of sensing a physiological signal, micro-stimulation, and wireless data/command transmission. Coverage includes analog front-end circuits for bio-signal acquisition, power management circuits for power and data communication, micro-stimulator circuits for neuromodulation, and digital signal processing circuits for data demodulation and control, as well as a variety of implantable applications, such as cardiac pacemakers, cochlear implants, retinal prostheses, functional neuromuscular stimulation (FNS) systems, and deep brain stimulators.