An efficient RNM compensation topology with voltage buffer and nulling resistors for large-capacitive-load three-stage OTAs

This work proposes and develops an original compensation approach for low-power three-stage operational transconductance amplifiers driving large capacitive loads. The proposed solution is based on the basic reversed nested Miller compensation and exploits a voltage buffer and two nulling resistors in the compensation network, along with a feedforward stage to improve slewing and settling performance. A well-defined design procedure using the loop gain phase margin as the main design parameter is also developed. Simulations on a three-stage amplifier are carried out and are found to be in excellent agreement with the theoretical analysis, showing a significant improvement of the proposed approach over traditional compensation strategies in terms of small-signal and large-signal performance.