Low Output Voltage Closed-Loop Current Source for Neural Stimulation

This paper analyses a closed-loop current source circuit, conducting a comprehensive stability study, and proposes design guidelines for achieving optimal energy efficiency. Specifically, the proposed methodology leverages the reduced drain-body voltage of a transistor working in the triode region to minimise the minimum output voltage required for the current source to operate properly. Using this methodology, a current source circuit intended for neurostimulation applications is designed in a commercially-available 130nm CMOS technology. The circuit achieves a minimum operating output voltage of just 90mV, improving on previous reported results from the literature.