Taken into account portable applications, where users are requiring larger durability of a single battery, in this paper the design of a linear differential-pair is presented. This circuit (hereafter named basic-block) is sizing according technological design rules of a 1.2?m CMOS fabrication process. Even when the basic-block is biased with 5V, and the same is true for the whole system, the power supply is actually a 1.5V battery. In this research we are assuming that the maximum driven current is of the order of 1mA.