1. A sense amplifier in a programmable resistive memory comprises: a reference branch having at least a first MOS transistor of a first type, the first MOS transistor having a source terminal coupled to a first supply voltage terminal or to a drain of another MOS transistor of the first type in series therewith, gate terminal(s) coupled to drain terminal(s) of the same first MOS transistor in series, if provided, and both the gate terminal and the drain terminal being coupled to a drain terminal of a second MOS transistor of a second type, the second MOS transistor having a gate terminal coupled to a bias supply voltage terminal, a source terminal coupled to a reference resistor and through the reference resistor further couples to a diode and to a second supply voltage terminal; a sensing branch having at least a third MOS transistor of the first type, the third MOS transistor having a source terminal coupled to the first supply voltage terminal or to a drain of another MOS transistor of the first type in series therewith, a drain terminal coupled to a drain terminal of a fourth MOS transistor of the second type, the fourth MOS transistor having the gate terminal coupled to the bias supply voltage terminal, a source terminal coupled to a programmable resistance device cell and through the programmable resistance device cell further coupled to the second supply voltage terminal, the programmable resistance device cell having a programmable resistance element coupled to a diode as program selector, wherein the gate terminal(s) of the third MOS transistor and, if provided, the another MOS transistor of the first type in series therewith in the sensing branch are coupled to the gate terminal(s) of the first MOS transistor and, if provided, the another MOS transistor of the first type in series therewith in the reference branch in the same serial order; and wherein the resistance difference between the reference resistor and the programmable resistance element is sensed through the drain terminal of the third MOS transistor in the sensing branch into a logic level.