A series regulator circuit includes one or more transistors each having a channel with one end coupled to an input node to receive an input voltage and another end coupled to an output node, and having a control node to receive a control voltage, a control circuit configured to adjust the control voltage in response to a voltage of the output node such that the voltage of the output node is set equal to a voltage setting selected by an output voltage setting signal, and a switch circuit configured to change an operating condition, excluding the control voltage, of the one or more transistors in conjunction with a change in the voltage setting of the output node.