Design of operational transconductance amplifiers with improved gain by using graded-channel SOI nMOSFETs

In this paper is presented, for the first time, the design of a single-stage operational transconductance amplifier (OTA) implemented with graded-channel (GC) SOI nMOSFETs. Different design conditions were taken in account, such as similar power dissipation, transconductance over drain current ratio and die area. Comparisons with OTAs made with conventional SOI transistors are performed, showing that the GC OTAs present larger open-loop gain without degrading the phase margin, unit gain frequency and slew rate. GC OTAs can also provide the mentioned improvements while simultaneously reducing the required die area. Circuit simulations and experimental results are used to support the analysis.