A circuit apparatus for providing an AC voltage to a load. The apparatus may include: a first, second, third and fourth switch, wherein the first switch is connected between a first node and a first terminal of the second switch and the fourth switch is connected between a second node and a first terminal of the fourth switch; a voltage source, wherein the voltage source is electrically connected between the first node and the second node; a resistive divider connected across the voltage source; a first resistor connected across the first switch a second resistor connected across the third switch; first connecting means for configurably connecting a second terminal of the second switch to the second node; second connecting means for configurably connecting a second terminal of the third switch to the first node; and third connecting means for configurably connecting the second terminal of the second switch in series with the second terminal of the third switch.