Citation: Ramirez-Angulo, J.; Diaz-Armendariz, A.; Molinar-Solis, J.E.; Diaz-Sanchez, A.; Huerta-Chua, J. Simple Technique to Improve Essentially the Performance of One-Stage Op-Amps in Deep Submicrometer CMOS Technologies. J. Low Power Electron. Appl. 2023, 13, 4. https://doi.org/10.3390/ jlpea13010004 Academic Editor: Andrea Acquaviva Received: 5 October 2022 Revised: 27 December 2022 Accepted: 29 December 2022 Published: 4 January 2023 Copyright: © 2023 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). Journal of Low Power Electronics and Applications Article Simple Technique to Improve Essentially the Performance of One-Stage Op-Amps in Deep Submicrometer CMOS Technologies Jaime Ramirez-Angulo 1, * , Alejandra Diaz-Armendariz 2 , Jesus E. Molinar-Solis 3 , Alejandro Diaz-Sanchez 4 and Jesus Huerta-Chua 1 1 Electronics Dept., Instituto Tecnologico Superior de Poza Rica, Poza Rica 93239, Mexico 2 Intel Guadalajara, Zapopan 45017, Mexico 3 Electronics Dept., Tecnologico Nacional de Mexico/ITCG, Cd Guzman 49100, Mexico 4 Electronics Dept., Instituto Nacional de Astrofisica, Optica y Electronica, Tonantzintla 72840, Mexico * Correspondence: jramirezangulo@gmail.com; Tel.: +1-915-474-4388 Abstract: A comparative study of one-stage-amp performance improvement based on simulations in 22 nm, 45 nm, 90 nm, and 180 nm in deep submicrometer CMOS technologies is discussed. Generic SPICE models were used to simulate the circuits. It is shown that in all cases a simple modification using resistive local common mode feedback increases open-loop gain and gain-bandwidth product, peak output currents, and slew rate by close to an order of magnitude. It is shown that this modi- fication is especially appropriate for its utilization in current CMOS technologies since large factor improvements were not available in previous technologies. The OTAs with resistive local common mode feedback require simple phase lead compensation with a very small additional silicon area and keep supply requirements and static power dissipation unchanged. Keywords: resistive local common mode feedback; class AB CMOS op-amps; mixed-signal circuits 1. Introduction Deep submicrometer CMOS technologies use sub-volt supply voltages that do not allow the use of cascode transistors in the output branch of op-amps. This is due to the fact that as feature sizes have decreased threshold voltages have not scaled down at the same rate as the supplies and they are a significant fraction of the supply voltages in current CMOS technologies. For this reason, cascode transistors in the output branches would seriously limit the output signal swing and are avoided. The lack of cascode transistors leads to low open-loop gains A ol in one-stage op-amps (also denoted OTAs) on the order of A ol =g m r o /2 = A/2, where g m is the small signal transconductance gain, r o the output resistance and A =g m r o the intrinsic gain of a MOS transistor in a given technology. The resulting open-loop gain of a non-cascoded gate-driven one-stage op- amp (Figure 1a) is only typically around 25–30 dB. This results in op-amps with very poor accuracy since the open-loop gain of an op-amp determines its accuracy for closed loop applications. Two-stage Miller op-amps can be used to overcome the problem and to achieve a higher open-loop gain A ol = [(g m r o ) 2 ]/2 (approximately 50–60 dB) but they require an area-intensive Miller compensation capacitance C c whose value is typically similar to the load capacitance C c =C L . Nested Miller compensated multistage op-amps can achieve higher open-loop gains but require complex compensation schemes which limit seriously their gain-bandwidth product or GB [1] and also require several silicon area-intensive capacitances. Assuming a typical design with C c =C L , both, one- and two-stage op-amps are characterized by a gain-bandwidth product given by the same expression GB = (1/2π)(g m /C L )[2]. In [3], a very simple scheme using resistive local common mode feedback (RLCMFB) was used to increase A ol and GB of a non-cascoded J. Low Power Electron. Appl. 2023, 13, 4. https://doi.org/10.3390/jlpea13010004 https://www.mdpi.com/journal/jlpea