Flexible charge balanced stimulator with 5.6 fC accuracy for 140 nC injections

Electrical stimulations of neuronal structures must ensure net injected charges to be zero for biological safety and voltage compliance reasons. We present a novel architecture of general purpose biphasic constant current stimulator that exhibits less than 5.6 fC error while injecting 140 nC charges using 1.4 mA currents. The floating current sources and conveyor switch based system can operate in monopolar or bipolar modes. Anodic-first or cathodic-first pulses with optional inter-phase delays have been demonstrated with zero quiescent current requirements at the analog front-end. The architecture eliminates blocking capacitors, electrode shorting and complex feedbacks. Bench-top and in-vivo measurement results have been presented with emulated electrode impedances (resistor-capacitor network), Ag-AgCl electrodes in saline and in-vivo (acute) peripheral nerve stimulations in anesthetized rats.