A compound current cell, with n-type, p-type, and bipolar properties, is proposed in this brief and utilized in a current-steering digital-to-analog converter (DAC) to satisfy the application of rail-to-rail voltage sources. In addition, the DAC with cells also has a high-speed fashion. Therefore, this brief presents a 6-bit CMOS current-steering DAC with cells for both communication and rail-to-rail voltage-source applications. Moreover, the effective output voltage step size is improved by appropriately switching these cells and connecting one of the gain control resisters, resulting in an about 6.4-mV step size in a 1.2-V supply. Furthermore, this DAC was implemented in a standard low-power 90-nm 1P9M CMOS technology with the active area of 0.045 \mm^2. The measured spurious-free dynamic range is more than 36 dB over the Nyquist frequency at 3 GS/s and the DAC consumes 8.32 mW with a near-Nyquist sinusoidal output at the sampling rate of 3 GS/s. [ABSTRACT FROM AUTHOR]