Band-gap reference voltage generator

A band-gap reference voltage generator comprises an operational amplifier comprising a first input and a second input, the first input being coupled to a first feedback network and the second input being coupled to a second feedback network both coupled to an output of the operational amplifier providing a reference voltage. The first feedback network contains an emitter-base junction of first bipolar junction transistor and the second feedback network contains an emitter-base junction of second bipolar junction transistor. A selectively activated current supply supplies a bias current to the operational amplifier, the current supply being deactivatable in a substantially zero power consumption operating condition for turning the reference voltage generator off. A start-up circuit activated upon start-up of the reference voltage generator for a fixed, prescribed time interval forces a start-up current to flow through the first bipolar junction transistor means.