A digital-to-analog converter based on differential-quad switching

A high-conversion-rate high-resolution oversampling digital-to-analog converter (DAC) for direct digital modulation is addressed in this paper. A new type of switching scheme, called differential-quad switching, is presented. To verify the feasibility of this scheme, essential parts with some auxiliary circuitry for interfacing were fabricated in a 0.8-mum CMOS technology. Measured results show that the switching scheme provides 11-b resolution at 100 MSamples/s and 6-b at 1 GSamples/s. The degradation in signal-to-noise ratio is not observed for the variation of the supply voltage down to 1.5 V, which means the proposed scheme is suitable for low-voltage applications.