A 10 bit 50 MS/s dual mode CMOS D/A converter fabricated with 1 μm CMOS technology was described. One mode is normal, another is power-save mode, in which a modified look-ahead circuit is designed to reduce power. The D/A converter was fabricated by using single-poly double-metal standard digital process. The integral nonlinearity error is less than 0.46 LSB. and the differential nonlinearity error is less than 0.03 LSB in the power-saving mode. The settling time to ±0.1% is less than 20 ns. The D/A converter has a single power supply of 5 V, and dissipates 250 mW at 50 MS/s when the input is 1023, while it dissipates 20 mW when the input is zero. The circuit chip size is 1.8 mm×2.4 mm.