Introduction

Implantable medical devices, such as pacemakers, spinal cord stimulators, and cochlear implants, play increasingly important role in saving and improving the quality of people’s lives. Circuit design is one of the important enabling technologies for those devices. It is helpful for the circuit designers to understand the uniqueness of implantable medical devices in order to make big contribution. Understanding the challenges of the neural interface-associated circuit design considerations is critical for successful medical devices. Electrodes are used to detect neural signals; however, electrodes are not ideal. The electrode performances, for both matching and impedance values, are typically beyond the control of circuit designers. Generally, improving input impedance and common-mode rejection ratio helps for both cases. Battery replacement for implantable devices often requires an additional surgery and can cause many complications. Currently, wireless powering through inductive link is still the main method for implant with rechargeable battery.