Analog digital converter

Analogue-digital converter with one input to receive an analogue voltage Vin to be converted, wherein it comprises three main reference voltages VR(i-1), VR(i), VR(i+1) and three differential amplifiers (ADA, ADB, ADC), each receiving on their first input, the voltage to be converted Vin variable between two extreme values Vext1 and Vext2 outside the interval between the main reference voltages, each of the amplifiers receiving one of the main reference voltages on second input, each amplifier supplying two output voltages (VAa, VAb;

• VBa, VBb;
• VCa, VCb) that vary symmetrically as a function of the voltage Vin, almost linearly about an average value Vm that is identical for the three amplifiers and that is obtained as an amplifier output when voltages on the two inputs of this amplifier are equal, the output voltages varying monotonically as a function of Vin for values of Vin between the extreme values Vext1 and Vext2, the converter also including a first interpolation circuit (CIT1) receiving the six amplifier output voltages and supplying four rank 1 interpolation voltages (V1a, V1b, V'1a, V'1b), variable as a function of Vin, according to a function that is near-sinusoidal for values of Vin between the main reference voltages, identical in amplitude for the four voltages but is out of phase, and representing a single sine period, the four interpolation voltages varying inversely in pairs, two of them (V1a, V1b) o passing through an average value and one of the two others (V'1a, V'1b) with a maximum and the other with a minimum when the voltage Vin is equal to any one of the three main reference voltages.