US Patent 7027860 Microstimulator neural prosthesis

A microstimulator or neural prosthesis is powered and operative in response to an externally applied RF signal which includes a power component and control component. A slow rise time storage circuit stores RF power during a charging period and a fast rise time triggering circuit responsive to a fast rise time input triggers the device for producing output pulses following a selected delay time. The duration of the delay controls the current level of the output pulses.