Patent ID: 7408391

Claim:
A charge pump comprising: a pull-up circuit which generates pull-up current that increases voltage at a charge pump output; a pull-down circuit which generates pull-down current that decreases voltage at the charge pump output; an operational amplifier having a first input and a second input, the first input coupled to the charge pump output and the second input coupled to a current carrying electrode of a master transistor of a current mirror, the operational amplifier output coupled to a selected one of said pull-up circuit and said pull-down circuit, the operational amplifier output also coupled to the control electrode of die transistor, the operational amplifier adjusting a voltage level at the operational amplifier output dependent on a voltage difference between the inputs to minimize the voltage difference between the inputs and decrease the difference between the pull-down current and the pull-up current; a reference current source for mirroring variable current in the other one of said pull-up circuit and said pull-down circuit, the reference current source including a programmable array of transistors; and a startup circuit coupled to a node at the charge pump output said startup circuit for setting the voltage at said node, during power-up the charge pump, to a voltage level below the power supply voltage.