The high CMRR and PSRR folded-cascode operational amplifier
Xi Li · Electronic Design Engineering · 2014
According to the fact that common mode rejection ratio and power supply rejection ratio are usually low in traditional operational amplifier, a differential input structure of folded-cascode operational amplifier was designed. Two stages of structure was adopted in the design of the whole circuit. The first stage is a differential structure folded cascode amplifier using MOS transistors as the resistors,further increasing the gain,CMRR, and PSRR of the circuit; The structure of common source amplifier using NMOS as load can dramatically increase the gain and output swing..Based on LITE-ON40V 1.0μm process, the Folded-cascode operational amplifier was designed and simulated by the use of Spectre. The simulation results indicate that the whole circuit can achieve up to 125.8dB gain and 62.8° phase margin. Moreover, the common mode reject ration and power supply rejection ratio are 140.9dB and 25.5dB respectively.