A Robust and Scalable Constant- Rail-to-Rail CMOS Input Stage With Dynamic Feedback for VLSI Cell Libraries

Abstract—In this paper, we propose a robust and scalable con-stant- rail-to-rail CMOS input stage for VLSI cell libraries. The proposed circuit does not rely on the characteristics and par-ticular operation (strong, moderate, and weak inversion) regions of the input transistorsand is insensitive tomismatches between p- and n-channel devices. Only standard CMOS transistors are used in the circuit without any special devices, such as floating-gate or deple-tion-mode transistors. Very small variations (less than %) have been achieved without sacrificing the large-signal behavior. The proposed circuit is proveneffective for both long- channel and deep sub-micron CMOS technologies and is suitable for VLSI cell libraries, audio/video, embedded mixed-signal system-on-chip (SoC), and other applications. A prototype amplifier with rail-to-rail input common-mode range has been designed and fabricated in a standard 0.35- m CMOS technology. Experimental results confirm the effectiveness and robustness of proposed techniques. Index Terms—CMOS analog integrated circuits, constant-, constant slew rate, operational amplifiers, rail-to-rail