Variable-gain amplifier with high linearity as to gain variations
A variable-gain amplifier includes an amplifier stage (17); an attenuating network (14a, 14b) receiving an input signal (V I ) ; a plurality of transconductance stages (15), connected between respective nodes (14a1, 14a2, ..., 14aN, 14b1, 14b2, ..., 14bN) of the attenuating network (14a, 14b) and the amplifier stage (17), wherein each of the transconductance stages (15) has a differential circuit (20), configured to supply differential currents (I D1 , I D2 ) to the amplifier stage (17); and a gain-control circuit (16) for controlling the transconductance stages (15) according to an electrical control quantity (V c ). Each of the transconductance stages (15) further includes a current-divider circuit (21) associated to the differential circuit (20) and controlled by the gain-control circuit (16) so as to divide the differential currents (I D1 , I D2 ) between the amplifier stage (17) and a dispersion line (33) proportionally to the control quantity (V C ).