In an apparatus in which an electrical interconnection interconnects stacked active and passive layers, switches, including at least first, second, third, and fourth switches, on the active layer define a switching network that, when connected to a fly capacitor on the passive layer, define a circuit having a first node connected to the first and second switches and to a first terminal of the fly capacitor, a second node connected to the second switch and third switches, and a third node connected to the third switch and fourth switches and to a second terminal of the fly capacitor.