Patent ID: 7450987

Claim:
An implantable pulse generator for generating electrical pulses for stimulation of tissue of a patient, the implantable pulse generator comprising: a controller for controlling operations of the implantable pulse generator; a voltage multiplier for selectively generating a plurality of voltages; a cathode node and an anode node; switching circuitry for controllably connecting the cathode node and the anode node to one or more outputs of the implantable pulse generator, the anode node being coupled to the voltage multiplier; output driver circuitry for providing constant current for respective pulses output from the implantable pulse generator, wherein the output driver circuitry comprises: (i) a transistor disposed between the cathode node and electrical ground of the implantable pulse generator; (ii) an operational-amplifier for providing a signal to a gate of the transistor to control a resistance of the transistor, the operational-amplifier comprising a first input and a second input, the first input of the operational amplifier receiving feedback from the transistor to limit current flow through the transistor; and (iii) circuitry for communicating a control signal to the second input of the operational amplifier; wherein, for generation of each stimulation pulse, the controller is operable to control the circuitry for communicating to communicate a first signal to the second input of the operational-amplifier to lower a resistance of the transistor before current is delivered to the patient by the output driver circuitry, to communicate a second signal to the second input to control an amplitude of a respective pulse during current delivery, and to temporarily cease to communicate a signal to the second input after delivery of current to the patient.