Low-power operational transconductance amplifier with slew-rate enhancement based on non-linear current mirror

Abstract

This paper presents a high slew-rate operational transconductance amplifier (OTA) based on a non-linear current mirror which dramatically reduces the quiescent current. The proposed circuit achieves less quiescent current than previously proposed architectures since no additional bias branches are needed. The compactness of the proposed architecture does not require so much silicon area as other more complex adaptive bias architectures. The proposed technique is compared with previous state of the art high slew-rate architectures. Additionally, this novel architecture was used to design a non-symmetrical OTA which was part of the feedback loop of a switched-capacitor DC---DC converter. This OTA occupies 420 μm2 fabricated in a 130 nm technology. Measurements results are presented showing that a slew-rate enhancement, from 1.5 to 535 mV/μs, is achieved in an OTA biased with 50 nA and loaded with 50 pF.