A high voltage, constant current stimulator for electrocutaneous stimulation through small electrodes

A high-voltage stimulator has been designed to allow transcutaneous stimula tion of tactile fibers of the fingertip, The stimulator's output stage was based upon an improved Howland current pump topology, modified to allow hig h load impedances and small currents. The compliance voltage of approximate ly 800 V is achieved using commercially available high-voltage operational amplifiers. The output current accuracy is better than +/-5% over the range of 1 to 25 mA for 30 mu s or longer pulses. The rise time for square pulse s is less than 1 mu s, High-voltage, common-mode, latch-up power supply pro blems and solutions are discussed. The stimulator's input stage is opticall y coupled to the controlling computer and complies with applicable safety s tandards for use in a hospital environment. The design presented here is fo r monophasic stimulation only, but could be modified for biphasic stimulati on.