The invention relates to the domain of turbo decoders. Such a decoder comprises a first decoder (14) and a second decoder (16), each decoder being able to calculate extrinsic output data from extrinsic input data coming from the other decoder. The decoding circuit according to the invention comprises a single memory (31) for storing the extrinsic data. When a decoder calculates an extrinsic output data from an extrinsic input data coming from the other decoder and stored in the single memory at a certain address, this extrinsic output data is then written at this same address.