Design Of A Rail-to-Rail Operation Amplifier Used By Multi-Mode High-Efficiency DC/DC Adapter At Low Potential

With the development of integrated circuit,the design of analog device become more and more urgent.Operation Amplifier(Op Amp) is a widely applied analog device.The input impedance of an ideal Operation Amplifier is supposed to be infinite.The output of an ideal Operation Amplifier is supposed to be zero. An ideal Operation Amplifier has infinite common-mode rejection.And also ideal Operation Amplifier will amplify signals of any frequency with equal gain. However as the voltage of the electrical engineering power supply becoming lower and lower, sometimes,the traditional Operation Amplifier could not meet the needs of market. Therefore,a kind of Operation Amplifier which called Rail-to-Rail CMOS Operation Amplifier turned out.Of which,the input circuit would allow the range of the voltage change from"gnd"to"vdd",and the Rail-to-Rail structure also can drive impedance that is lower.The product of gain and bandwidth would be higher.An Operation Amplifier always based on the Bipolor Junction Transistor(BJT) differential pair . which consists of two matched transistors,their emitters are joined together and biased by a Constant-current source.the latter is usually implemented by a transistor circuit of the type.the differential pair certaily responds to difference-mode or differential signals.A typical BiCMOS process consists of a standard CMOS flow,with the addition of a minimum number of steps to construct adequate bipolor transistor.BiCMOS technologies seek to merge the best of both CMOS and Bipolor Junction Transistor.