The Research Of Low Drop-out Linear Regulator Based On CMOS Technology

Recently, with the development of the technology of IC design and power management, low drop-out linear regulator has become more and more popular. It has advantages such as simple structure, low noise and small static power loss, so it is widely applied in cellular electronic products such as PDA, MP3 player, portable computer, communication and medical equipments and test instruments. Nowadays, the main markets of power management are occupied by foreign products, it is very meaningful to develop our own products in order to recapture enormous market share.Firstly, the background and meaning of this project are discussed, and then the actuality and trend of development of LDO as well as the expectant technical goals are also presented.Secondly, the basic theory of LDO is analyzed in detail, including its framework, operating principle, performance goals, and design considerations for those goals.Thirdly, a two-order error operational amplifier and band-gap voltage reference based on self bias current source is designed with CMOS technology. A PMOS transistor is adopted as the pass element, and its sizes are calculated. Then the performances of amplifier and voltage reference are simulated with HSPICE.Fourthly, the stability characteristics of LDO are analyzed,and the necessary condition for stability compensation is pointed out. The principle of frequency compensation methods are discussed in detail. The stability is compensated by a method called VCCS based on capacitive feedback.Finally, a LDO linear regulator is developed with CMOS technology. The drop-out voltage, static current, linear regulation are simulated with HSPICE, and the simulation results show the feasibility of the proposed methods.