A current generator circuit for tripolar stimulation and insensitive to temperature and supply variations

We present a current generator circuit which supplies two anodic currents for tripolar nerve stimulation. Depending on applications and the more convenient method of adjustment, the difference of the two anodic currents can be programmed using either of the two different modes. The reference current circuit in the current generator utilizes a gate-drain tied depletion transistor working in the triode region as the degenerating resistor in the Beta-multiplier topology. The negative temperature coefficient of the depletion transistor reduces the total sensitivity of the output current to temperature variation. The proposed current generator circuit is also stable over a wide range of supply voltages. Simulated results using a 0.6-μm CMOS process are presented. The temperature coefficient and power supply rejection ratio of the current generator are less than 0.06%/°C and 2%/V, respectively.