This paper presents a 1.3mA current stimulator integrated circuit (IC) with closed-loop, active charge balancing for nerve interfacing applications. The stimulator employs two current-based digital-to-analog converters (DACs), one each for anodic and cathodic phases, with binary-weighted transistors and 2b-programmable least-significant bit (LSB) currents. The biphasic, cathodic-leading, stimulus current pulse amplitude is 5b-programmable in four ranges of ∼ 12–341μA, 23–682μA, 32–992μA, and 42–1,300μA. A low-power (∼10μW), active charge balancer monitors the site voltage after each stimulus cycle and, if necessary, injects positive or negative current pulses via two 3b auxiliary DACs to bring the site voltage back within a userset safety window. All digital circuitry operate from 3.3V, whereas the stimulator output stage operates from 5V with a stimulus site common-mode voltage of 3.3V for better use of the available voltage headroom in cathodic-leading, single-supply stimulation. A prototype chip is fabricated in 0.5μm 2P/3M CMOS, and measured results from benchtop electrical characterization of the chip are presented.