Abstract: A power-on-reset circuit for delivering a power-on-reset pulse when a supply voltage ramps up from zero to a predetermined voltage includes a pull-down circuit portion for connecting an output node of the power-on-reset circuit to ground when the supply voltage reaches a predetermined upper threshold voltage and a pull-up circuit portion for connecting the output node to the supply voltage when the supply voltage reaches a predetermined upper threshold voltage. The pull-up circuit portion includes a transistor whose gate is polarized by a reference voltage taken at the terminals of a precision resistance traversed by a current delivered by a current generator, where the current is preferably a band-gap current proportional to the temperature of the circuit. The power-on-reset circuit is particularly suitable for microprocessors.