There is described an 
electronic interface device (1) for reading an output 
signal and controlling and conditioning a three-
electrode amperometric sensor (S). The device (1) may be used with a sensor having an electro-chemical 
cell comprising a 
reference electrode (RE) configured to supply a constant 
cell electric potential to the 
electrochemical cell; a 
working electrode (WE) at which oxidation or reduction reactions occur, connectable to a first reference 
voltage; and a collector 
electrode (CE) configured to deliver or receive 
electric charge carriers. In the electro-chemical 
cell, a 
cell impedance (Zcw) is always present between the 
working electrode (WE) and the collector 
electrode (CE).The device (1) comprises an 
operational amplifier (U), having a non-inverting input (u1), adapted to receive a biasing 
electric potential (VBIAS) depending on the type of electrochemical reaction of the sensor, and an inverting input (u2) connectable to the 
reference electrode (RE) of the sensor. The 
operational amplifier is adapted to operate in a feedback configuration to supply the 
reference electrode (RE) with the aforementioned constant cell 
electric potential on the basis of the biasing electric potential (VBIAS).The device (1) further comprises a first MOS 
transistor (M1), having a first MOS gate terminal (G1) connected to the output of the 
operational amplifier (U), a first MOS drain terminal (D1), connectable to a second reference 
voltage, and a first MOS source terminal (S1), connectable to the collector electrode CE of the sensor (S) to receive or supply a first MOS 
transistor channel current (I1) representative of (for example equal to) the cell current (I) which is generated in the amperometric sensor (S).The device (1) further comprises a second MOS 
transistor (M2) having a second MOS gate terminal (G2) connected to the output of the operational 
amplifier (U) and to the aforementioned first MOS gate terminal (G1), a second MOS source terminal (S2), connectable to the first reference 
voltage by means of a first 
resistor (R1), and a second MOS drain terminal (D2), connectable to the second reference voltage (for example, through a 
resistor R2 which allows the reading of a voltage proportional to the current).The value of the first 
resistor (R1) is lower than the 
cell impedance (Zcw) so that the second MOS 
transistor channel current (I2) depends on the first MOS 
transistor channel current (I1), representative of the cell current (I) of the sensor, through a 
nonlinear gain dependent at least on the value of the first resistor (R1).The second MOS transistor (M2) is of the same type as the first MOS transistor (M1).Also described is a method for reading an output and 
control signal of a three-electrode amperometric sensor, carried out by the aforementioned device.