Two-stage class-AB OTA using super class-AB RFC and multi-path scheme

This paper presents a new design idea for two-stage class-AB operational transconductance amplifier (OTA). In the proposed OTA, increasing transconductance of the first stage is achieved using super class-AB recycling folded cascode. In addition, active loads are involved in improving the transconductance. Increasing the transconductance, as well as using the multi-path scheme, leads to an enhanced DC gain. The multi-path scheme is provided for both stages. A non-linear current mirror is employed to boost the current of the output stage. As a result, slew rate (SR) is increased. The proposed circuit is simulated in a 0.18-μm CMOS process using the Cadence software, and its output performances are evaluated. The supply voltage of the proposed OTA is chosen as 1.8 V. Post-layout and Monte Carlo simulation results indicate that the output performances of the proposed circuit are better compared to that of existing solutions. The proposed OTA exhibits 93-dB DC gain. The proposed OTA and the existing two-stage class-AB OTA have the same power consumption of about 3 mW, but the improvement in SR and unity-gain bandwidth in the proposed structure is 86% and 48%, respectively.