A three-stage class AB operational amplifier with enhanced slew rate for switched-capacitor circuits

In this paper, a three-stage class AB operational transconductance amplifier (OTA) with large slew rate is presented. The reversed nested Miller compensation technique is used to stabilize the proposed OTA, allowing the slew rate enhancement to be achieved by using class AB input and output stages. A flipped-voltage follower cell in the first stage in combination with a switched-capacitor level shifter in the last stage are utilized to implement the class AB operation. Circuit level simulation results are provided using HSPICE and a 90 nm CMOS technology which show 306 % enhancement in the large-signal FoM with approximately the same power dissipation compared to the class A OTA. The achieved settling time with 0.02 % accuracy for the proposed class AB and conventional class A OTAs are 7.5 and 15.3 ns, respectively.