A Charge-Balanced Monopolar Neural Stimulator by Utilizing Dynamic Current Replication Technique Achieving <1 nA Residual Average DC Current Error

This paper presents a monopolar neural stimulator using dynamic current replication technique based on switched-capacitor sampling. It employs dynamic current mirror circuits as the current source and the current sink to overcome the impact of process variation on current matching, achieve good charge balance and ensure the security of the monopolar neural stimulator. The proposed monopolar stimulator is implemented with a 0.18-μm 1.8 V/3.3 V standard CMOS process. The simulated results indicate that the current mismatch between the cathodic and anodic current is less than 0.21%, and the charge mismatch is below 0.33% within the entire stimulus current range (0.3 mA ~ 3 mA). The corresponding maximum residual average DC current error with shorting electrode discharge is less than 1 nA.