A super class-AB OTA with high output current and no open loop gain degradation

Abstract

A scheme to achieve simultaneously extremely high slew rate improvement and avoiding open loop gain degradation in one stage super class-AB op-amps is introduced. It overcomes the serious shortcoming of super class-AB OTAs that show very high output current enhancement factors at the expense of degrading the open loop gain. The proposed scheme uses dynamically biased cascode transistors to avoid gain and slew rate degradation. Experimental results of a fabricated super class-AB OTA in 180 nm CMOS technology with open loop gain of 67 dB, a factor two improvement in GBW and a current enhancement factor of 270 verify the proposed scheme.