Power analysis and optimal design of opamps for oversampled converters

In this paper, we address three issues related to the design bf opamps for oversampled converters: the theoretical minimum-power bound for an ideal op amp, the best opamp choice in terms of power dissipation, and the best desi gn strategy to reduce power dissipation. To be able to do so, we develop a model that captures the dynamics of the integrator inside the modulator. Ba sed on this model, power dissipation for various opamp topologies is comput ed and compared with each other. We show that class-A opamps can consume on e to six times the current consumed by an idealized class-AB opamp, though the savings for practical class-AB opamps is likely to be lower. For high-r esolution applications, class-A topologies are most optimal, while for lowe r resolution lower power applications, class-AB opamps may be more suitable . We further demonstrate a design strategy with the help of an example that can be used to minimize the power dissipation for class-A opamps,