a controller configured to provide a first current and an additional current to a current mirror to rapidly charge a capacitance coupled to the current mirror, wherein the controller applies the additional current in response to a reference voltage; and

logic configured to provide the additional current to the current minor when a base voltage of the current minor is less than the reference voltage, the logic comprising a comparator and at least one logic gate, responsive to two control signals, the two control signals defining a time period during which the additional current is provided.