Multibit oversampled DAC with dynamic matching of current sources

Conventional binary-weighted and oversampling techniques are very popular methods of performing D/A conversions. However, the accuracy required in the component matching limits the resolution obtainable with a binary-weighted converter to ~8 bits, unless very sophisticated techniques (including selfcalibration) are used. Moreover, the resolution which can be achieved with an oversampled converter is limited by the oversampling factor actually obtainable for a predetermined signal bandwidth with any given integration technology. This paper presents a novel combined conversion approach, which takes advantage of the positive features of both the above techniques. The most significant bits (MSBs) are converted with the binary-weighted technique, while the least significant bits (LSBs) are converted with the oversampling technique