A Fully Integrated Fail-safe Stimulator Output Stage Dedicated to FES Stimulation

There is a great demand to reduce the volume of implantable multi-channel stimulators for functional electrical stimulation applications. Miniaturization is currently limited by the size of the large off-chip blocking capacitors that are required for safety. This paper describes a fail-safe stimulator output stage circuit utilizing the principle of high-frequency current-switching, which allows the blocking capacitors to be integrated on-chip. The proposed circuit is based on the bridge rectifier circuit, hence fully utilizing the bidirectional current through the blocking capacitor. The approach has been verified by post-layout simulations in a 1 μm CMOS SOI technology.