the inverted version of said first signal in said capacitor c is connected by a side to ground and by the other side to the non inverting terminal of the comparator 12 and to the switch 10 the voltage current converter 9 receives the control voltage vin and it provides a current proportional to said voltage vin when the signal vin controls to close the switch 10 and to open the switch 11 said current charges the capacitor c to the terminals of the capacitor c a voltage vc is present that is compared by the comparator 12 with a reference voltage vref so as to provide the output signal out when vc gt vref when the signal in controls to open the switch 10 and to close the switch 11 the charge contained in said capacitor c discharges toward the ground in fig3 in greater detail the schematic circuit of fig2 is shown the block 1 besides comprising the voltage current converter block 9 and the switch block 10 comprises also a block 13 connected to a supply line vcc particularly the voltage current converter 9 is realized by a sense amplifier 14 on the output of which is connected a n channel mos transistor 15 in source follower configuration and by a resistance r connected by a side to.