A transistor-only power-efficient high-frequency voltage-mode stimulator for a multichannel system

This paper proposes a fully implantable high-frequency switched-mode neural stimulator. The main circuit consists of 2N transistors for an N-electrode system in which all channels can be stimulated concurrently and independently. System simulations show that power efficiencies of 80% or higher are feasible over the full output range. The system is powered from a single-ended battery voltage and does not need external components. It uses the dynamic properties of neurons to filter the high-frequency signal such that the resulting stimulation becomes equivalent to that of traditional stimulation. The system has a voltage-mode output and therefore safety aspects such as charge cancellation are carefully considered. Also the influence of high-frequency mode operation is considered as far as available models allow. Using system-level simulations the functionality of the system is illustrated from circuit level down to axon level. Furthermore a discrete-component prototype is constructed to verify that the stimulation protocol is able to successfully induce activation in the tissue.