Calculation of Total Integrated Noise in Analog Circuits

Electronic noise is a significant and fundamental issue in the design of analog circuits. In the widely used class of switched-capacitor circuits, the noise metric of interest is the so-called total integrated noise. Closed-form expressions for this quantity are unavailable in literature for all but the simplest circuit configurations that involve first- and second-order noise transfer functions. The lack of these expressions has prevented design automation and performance optimization without relying on repetitive simulations. In this paper we provide a general formula for calculating the total integrated noise in arbitrary circuits. The results are applied to two popular operational transconductance amplifier (OTA) circuits; a two-stage Miller-compensated architecture and a two-stage cascode-compensated topology. Simulations show that the calculated noise for these circuits is in close agreement with SPICE simulations.