A device for converting a differential signal (Vin1, Vin2) to a single signal (Vout) is described. The device comprises at least one pair of transistors (Q1, Q2) having equal transconductance gain (gm) and which are arranged according a differential stage configuration. The transistors (Q1, Q2) have the differential signal (Vin1, Vin2) in input at the drivable terminals, have first non drivable terminals coupled respectively to first terminals of a first (R1) and a second (Rout) passive elements having second terminals connected with a first supply voltage (VDD), second non drivable terminals coupled to a second supply voltage (VEE) lower than the first supply voltage (VDD). The first terminal of the second passive element (Rout) is the output terminal (OUT) of the device. The last comprises a further transistor (Q3) having a first non drivable terminal connected with the output terminal (OUT) of the device, a second non drivable terminal coupled with said second supply voltage (VEE) and the drivable terminal connected with the first terminal of the first passive element (R1). The further transistor (Q3) has such a transconductance gain (gm3) that the product of said transconductance gain (gm3) by said first passive element (R1) is unitary.