A standby regulator circuit includes a standby bias circuit and a standby operational amplifier. The standby regulator circuit provides a standby regulated control voltage to a multiplexer. A regular operational amplifier provides a regulated control voltage to the multiplexer. During regular operation, the multiplexer selects the regular operational amplifier and selects the standby regulator circuit in a low-power mode. The multiplexer couples to a native pass transistor gate having a threshold voltage about equal to 0 V. The native pass transistor provides a regulated output voltage with relatively low-level input control voltages. In low-power mode, a power-down signal, provided to the multiplexer, smoothly transitions regulated control voltage from the regular operational amplifier to regulated control voltage sourcing from the standby operational amplifier. In low-power operation regular operational amplifier power is saved and the standby operational amplifier is appropriate for regulating the low threshold voltage native pass transistor.