98-dB Gain Class-AB OTA with 100 pF Load Capacitor in 180-nm Digital CMOS Process

Abstract

In this paper, a new two-stage class-AB operational trans-conductance amplifier (OTA) is proposed. Using active loads in the first stage and improved recycling structure, the effective trans-conductance of the first stage is increased. The nonlinear current mirrors boost the current of the second stage in the slewing mode, leading to the increase of the slew rate (SR). Exploiting the multi-path scheme and increasing the effective trans-conductance cause the OTA DC-gain to be enhanced. The proposed OTA has been fabricated using 1P6M 180-nm CMOS technology under 1.8 V supply voltage. The OTA exhibits 98 dB DC-gain and 21 MHz unity-gain bandwidth with a 100 pF capacitive load, consuming 3 mW from 1.8 V supply voltage.