In order to achieve a high input dynamic range as well as high CMRR and PSRR values and input impedance with the use of a single supply voltage (Vcc), the amplifier includes an input stage with two transistors (Q1, Q2) which are biased by a constant current (IP3, IP4), preferably of less than 1 microampere, and the collectors of the transistors (Q1, Q2) are kept at fixed reference voltages (VR1, VR2). The input signal (VIN) applied between the emitters (IN(-), IN(+)) of the transistors (Q1, Q2) is transferred to the terminals of a first resistor (R1) which is supplied with current (IR1) from a circuit (M7, A5, R3; M10, Q6, R4; M9, Q7, R5) which mirrors the current (IR1) into a second resistor (R6), from the terminals of which the output signal (VOUT) is taken. The preferred application is for forming interfaces for lambda probes fitted to catalytic converters for motor vehicles.