In certain embodiments, a circuit comprises a first voltage source configured to provide a supply voltage at an output of the first voltage source for a subcircuit. The circuit further comprises at least one second voltage source configured to provide output voltage to supply the subcircuit when the first voltage source is deactivated. The circuit further comprises an evaluation circuit connectable to an output of the at least one second voltage source, to a control input of the at least one second voltage source, and to the output of the first voltage source. The evaluation circuit is configured to adjust, based on the supply voltage at the output of the first voltage source, an output voltage of the at least one second voltage source.