A Constant- $g_{m}$ Constant-Slew-Rate Rail-to-Rail Input Stage With Static Feedback and Dynamic Current Steering for VLSI Cell Libraries

A constant-g_m input stage featuring both constant small signal and large signal behaviors over the entire input common-mode range is proposed in this brief. A novel static feedback loop is employed to minimize the N and P transconductance mismatch due to process and temperature variations. The output currents of the N and P differential pairs are dynamically steered to keep a constant g_m and a constant slew rate. The overall technique is independent of the operation regions of input transistors, and does not rely on the quadratic characteristics of input MOS transistors. A prototype chip was designed for a 0.35-mum CMOS technology with 3-V power supply. The experimental results demonstrate that a constant-g_m (plusmn3% variations) and a constant slew rate over the entire input common-mode range have been achieved