The proposed CMOS Low DropOut (LDO) regulator has been designed and simulated using ON semiconductor's 0.5µ CMOS process. This paper illustrates the design criteria and corresponding analysis relevant to LDO. The experimental result shows that, it regulates an output voltage at 3.3V from a 3.5V supply, with a minimum dropout voltage of 200mV at a maximum output current of 50mA using a reference voltage of 1.2V. The regulator provides a load regulation of 0.0152V/A, line regulation of 0.13mV/V. Efficiency of 93.27% is achieved. Detailed analysis of CMOS LDO has been presented.