advances on cmos folded-cascode operational transconductance

In this paper, a tutorial review on several structural improvements of the cmos folded-cascode operational transconductance amplifier (ota) is presented. after a brief discussion on the structure and operation of the conventional folded-cascode amplifier, its several architectural improvements are reviewed. these improvements include advances on class a and class ab folded-cascode amplifier s and recycling folded-cascode amplifier. afterwards, several improved class a and class ab recycling folded-cascode operational transconductance amplifiers are discussed, and finally some two-stage operational transconductance amplifiers based on the current recycling technique are reviewed. as it can be seen, many architectural innovations have been proposed to improve both small-signal parameters, including dc gain, unity-gain bandwidth, phase margin, and large-signal operation, which is usually characterized by slew rate in the proposed otas compared to the basic folded-cascode amplifier. current recycling, shunt current sources, cross-coupled transistors to realize local positive feedback paths, local common-mode feedback, flipped voltage follower cells to realize class ab operation, active current mirrors, and several other techniques have been utilized in the structural improvements of the basic folded-cascode operational transconductance amplifier. the achieved results are more promising and demonstrate substantial achievements in the design of operational transconductance amplifiers in low-voltage and more scaled nano-meter cmos processes.