Design of a Biphasic Current-Matching Neural Stimulator

A biphasic current-matching neural stimulator based on 0.18 μm CMOS process is presented. The stimulator can output biphasic current ranging from 5 μA to 160 μA and its stimulation pulse width can be adjusted from 17 μs to 250 μs. The proposed stimulator consists of a bandgap reference, a digital block for stimulus width control, the high-matching current drivers to produce adjustable biphasic current, and an on-chip voltage buffer. In order to achieve biphasic current matching, feedback loop is built in the circuit design to keep each current highly stabilized. The stimulation result demonstrates that this system can realize biphasic well-matched stimulation current. The error of the current matching is within 1.76%.