An analytical gm/ID‐based harmonic distortion prediction method for multistage operational amplifiers

Abstract

SummaryAn analytical stage‐based harmonic distortion (HD) analysis method for multistage operational amplifiers (Op Amps) is developed in this work. This work contributes two fundamental methods that make the analytical HD prediction possible at the circuit level. Firstly, we propose that the traditionally used first order small‐signal transistor quantities gm (transconductance) and go (output conductance) in the gm/ID design methodology for bulk complementary metal‐oxide‐semiconductor (CMOS) technology can be extended to the higher order quantities gm(k) and go(k) ( ). With proper normalization, these quantities become neutral to the device dimensions and operation currents, hence can be precharacterized by sweeping simulations and used as lookup tables. Secondly, we further develop analytical nonlinearity expressions for a set of commonly used amplifier stages, represented as the functions of the nonlinearity parameters gm(k) and go(k) of the transistors that form a stage circuit. A combination of these two fundamental methods on hierarchical nonlinearity modeling enables us to apply the existing analytical HD estimation methods for the stage‐form macromodels to predict the circuit‐level HD behavior, overcoming the need of running repeated simulations under device resizing and rebiasing. The proposed harmonic distortion analysis method has been validated by application to real multistage amplifiers, achieving HD prediction results in excellent agreement to fully transistor‐level circuit simulation results but with substantial speedup.

Fast Design Space Exploration and Multi-Objective Optimization of Wide-Band Noise-Canceling LNAs

“…All the previous methods require complex computations and large memory consumption, where many first, second and third derivatives will be required to be stored or computed. An equation-based nonlinearity calculation technique based on gm/ID was discussed in [16,17], but it suffers from limited accuracy due to the approximations made in the derivations.…”

Analysis of and Reduction in Noise in Current Measurement of XCP under the Laboratory Condition

“…Therefore, when a higher gain is required, several operational amplifiers are generally cascaded to form a high-gain operational amplifier to meet the multiple gain requirements. Since the electrode signal amplifying circuit inside the XCP sensor is actually composed of a three-stage amplifying circuit, noise is inevitably introduced [32,33]. In order to study the noise effect introduced by the amplifier circuit, the noise effect can be converted into a noise voltage.…”

Experimental Determination of Parameters of Nonlinear Electrical Load

“…However, more sophisticated approaches based on semiconductor converter models have also been extensively used [19]. The complexity of mathematical models leads to the limited use of analytical methods [20,21] and more extended use of simulation modeling, which makes it possible to obtain numerical solutions for the tasks [22,23]. In addition, it is often necessary to carry out rough estimates of network operation modes with nonlinear loads while maintaining sufficient accuracy for engineering practice.…”