Entire Input Common-mode Range Research Articles

A rail-to-rail input stage with constant signal behavior in 0.12 μm CMOS

This paper introduces a new fully differential low-voltage rail-to-rail input stage structure, which possesses a constant small- and large-signal behavior over the entire input common-mode range, and is suitable for low supply voltage applications in deep-submicron technologies. The proposed input stage is fabricated with two different opamp architectures in pure digital 0.12 μm CMOS technology for experimental verification. At ±0.5 V supply, the small-signal behavior variation is 5.45% across the supply rail. The large-signal behavior is constant at different input common-mode levels. The maximum current needed for the signal behavior regulation is only 90 μA.

A Constant-<formula formulatype="inline"><tex>$g_{m}$</tex> </formula> Constant-Slew-Rate Rail-to-Rail Input Stage With Static Feedback and Dynamic Current Steering for VLSI Cell Libraries

A constant-g <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">m</sub> 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 <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">m </sub> 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 <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">m</sub> (plusmn3% variations) and a constant slew rate over the entire input common-mode range have been achieved

A family of high-swing CMOS operational amplifiers

A family of high-swing CMOS operational amplifiers has been developed to maximize the available dynamic range with low supply voltages. Complementary differential pairs are used to achieve an almost rail-to-rail input common-mode voltage range. High linearity is obtained by summing currents so that the small-signal differential-mode voltage gain is constant over the entire input common-mode range. With a 5.0-V power supply, the total harmonic distortion is typically only 1% in a unity-gain configuration with a 4.5-V/sub p-p/ signal. The measured DC offset voltages versus input common-mode range track between the conventional and high-swing versions. These measurements suggest that the commonly feared crossover distortion may not be a problem when the current summation high-swing topology is used. The measured step response characteristics were excellent and exhibited no signs of phase mismatch crossover distortion for high-frequency signals. >