40 Abstract STMicroelectronics is a world- wide microelectronics company It installs its business in the sector of integrated circuits for several application such as automotive, home, industry, internet of things. Most of these applications are using today one or several microcontrollers. A widely used element to regulate power supply of microcontrollers cells is the Low drop Out regulator (LDO) :a class of voltage regulator. It uses a voltage reference and a feedback loop system to deliver constant regulated voltage and to protect cells from external fluctuation, noise and excursion. In this internship I have designed, and Simulated Analog circuit with the software Cadence Virtuoso.