Noise Effects in a Current Driver for a Neurostimulator

This paper presents the problems of realization of current driver. It provides a stable current amplitude required for electrical stimulation. To ensure the safety of the stimulation process, various publications tend to increase the output impedance of the current driver as high as possible. This improves the stability of the output current with load resistance variation. However, achieving excessively high output resistances is pointless as it will not lead to the desired current stabilization due to the presence of noise current. In this case, the circuit solution becomes unscalable and the chip area and power consumption increases. An algorithm for estimating the rational value of the current driver output resistance based on the RMS noise current at the output of the circuit is proposed. The presence of the output impedance limitation relaxes the size requirements of the current driver transistors and the gain of the operational amplifier. The proposed algorithm is verified by simulation in Cadence Design Systems software using 180 nm CMOS technology.