A new low voltage low power fully differential CMOS class AB current output stage with unique current drive capability

Abstract

ABSTRACT This paper presents a novel low-voltage low power fully differential class AB current output stage with high linearity and unique current drive capability. The proposed circuit is based on a simple and efficient structure to obtain high linearity by minimising the channel length modulation effect and also avoids cascade structure to act best in low-voltage applications. Giving the complete analyses and equations of the circuit, its properties are verified by Cadence using TSMC 0.18 µm CMOS parameters. In order to study its performance at the presence of non-idealities, Pre-layout and Post-layout both plus Monte–Carlo simulations are also performed. Under±0.9 V supply and 35 µA output bias current, it can deliver the ever high output current of ±350 mA with THD of −49 dB and output impedance of 2.8 MΩ, which leads to a unique high current drive ratio (Ioutmax/Ibias) of 10,000 and low consumed power of 150 µw in pre-layout simulation. In post-layout plus Monte–Carlo simulation, the results will be as ±320 mA output current, −42 dB THD, 2.2 MΩ output impedance, 40 µA DC current of the output branch, 8000 current drive ratio and 160 µw consumed power. These remarkable results prove the proposed novel COS not only as the unique one in the world but Longley ahead of the yet second rank COS by some unbeatable ratios as 11300×,14×,4× and3× in F T , I outmax , (Ioutmax/power), and current drive, respectively, that promise to keep it as the lead one for many years in low-voltage/power ultra-high current applications.