To satisfy higher and higher transmission rate and broadband requirement of modern communication, high-speed, low-resolution Digital-to-Analog Converters (DACs) becomes the key element. In this paper, the design of a 2 GS/s, 6 bit DAC without calibration for Ultra-wideband (UWB) applications, is presented. The DAC is based on current steering architecture and is segmented with 4 bit unary and 2 bit binary. To realize larger linear range and fast switching, the source degeneration switch is designed instead of the traditional differential switch. The DAC is designed and taped-out in SMIC 0.18 μm CMOS technology and the area is 975 μm☓775 μm. The wafer bonding measurement results shows that the DNL is 0.11 LSB, INL is 0.25 LSB. Under a clock frequency of 2 GHz, the DAC can achieve a SFDR of 51 dB for input signal of 6MHz, and a SFDR of 32.4 dB for Nyquist input while the power consumption is 79 mW.