A power efficient startup circuit for activating a bandgap reference circuit is disclosed. The startup circuit uses a voltage supply having a voltage level to initiate the flow of a startup current used to activate the bandgap reference circuit. When the bandgap reference circuit starts, the startup circuit slowly charges a capacitor using the voltage supply when the startup current is flowing. The startup circuit disables quiescent current when the bandgap reference circuit is activated and a voltage of the capacitor exceeds a value equal to the difference between the voltage of the voltage supply when powered on and a voltage threshold of a switching device which disables the quiescent current. The capacitor is discharged when the voltage supply is turned off.