ON THE POWER EFFICIENCY OF CASCODE COMPENSATION OVER MILLER COMPENSATION IN TWO-STAGE OPERATIONAL AMPLIFIERS

摘要

Optimization of power consumption is one of the main design challenges in today's low-power high-speed analog integrated circuits. In this paper, two popular techniques to stabilize two-stage operational amplifiers, namely, Miller and cascode compensations are compared from power efficiency point of view. To accomplish this, cascode-compensated topologies are basically analyzed to derive the required equations for the comparison. In the analysis, a new method to take into account the effect of transfer function zeros is proposed. By assuming that the zeros' magnitudes are fairly nondominant, the method increases the accuracy of the analyses. The relationships show that for the same specifications, cascode compensation is more power-efficient than Miller compensation, especially for heavy capacitive loads. This has been confirmed by SPICE simulations.