Reducing the supply voltage of operational amplifers and analog circuitry in general, isof great importance as it will ensure the future coexistence of analog and digital circuitson the same silicon die. While digital circuits greatly benefit from the reduction in featuresize and supply voltage, analog circuits on the other hand only beneft marginally becauseminimum size transistors cannot be used due to noise and offset requirements. This trendtowards low voltage and low power, effects the fundamental limits of operational amplifiers. The gain and bandwidth are restricted by minimum voltages and currents. Also thedynamic range is degraded by these strict limits. Upwards, the dynamic range is lowereddue to the reduced signal headroom as a result of reduced supply voltage. Downwards, thedynamic range is limited by larger noise voltages due to smaller supply currents. The onlyway to make the operational amplifer survive the trend towards lower supply voltageswithout deteriorate its characteristics, is by developing very effcient operational amplifertopologies that combines low voltage and low power operation and contemporary be assimple as possible to save die area.This thesis presents some of the main aspects of low voltage and low power operationalamplifers and their ability to work from rail to rail on both input and output. Theinput referred offset voltage was also characterized. Theory around input and outputstages are studied. A low voltage operational amplifer was processed in 0.35 um CMOS.Measurements were done on the operational amplifer and compared with the simulationresults.