Patent ID: 7176733

Claim:
A charge pump comprising: a pull-up circuit which supplies a pull-up current to increase voltage at a charge pump output; a pull-down circuit which supplies a pull-down current to decrease 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 drain of a transistor that supplies current to the pull-down circuit, the operational amplifier output coupled to the pull-down circuit and the gate of the 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; and a startup circuit coupled to the first input which sets the voltage at the first input to a voltage level below a power supply voltage during power-up of the charge pump.