Ricerc@Sapienza

A class-AB OTA (operational transconductance amplifier) topology
with rail-to-rail input common-mode range is proposed for application
in very low-voltage applications. High efficiency is achieved by
reusing transistors both for class-AB operation and for mirroring the
output currents, and a threshold lowering technique is applied to
allow supply voltages less than two threshold voltages. Simulations
in 40 nm CMOS technology show 41 dB gain at ±0.3 V supply
voltage, a unity-gain frequency of 8.8 MHz on a 5 pF load, class-AB

We present a low voltage approach to design an adaptive bias circuit for a class-AB input stage, and exploit it to design a fully-differential 0.6 V class-AB symmetrical OTA that also features cascode dynamic biasing and a class-AB CMFB circuit. Simulations in 0.13 μm CMOS technology show a 42x increase of the bias current when signal is applied, that yields a faster settling time with respect to a class-A OTA designed with the same static current.

An innovative low-voltage low-power complementary metal-oxide-semiconductor (CMOS) gain boosting approach is presented. It exploits complementary gate-driven gain boosting and adopts forward body bias, resulting in the minimum possible supply requirement of one threshold plus two saturation voltages, without requiring any additional current branch. The solution is also exploited in a rail-to-rail high-performance single-stage cascode operational transconductance amplifier (OTA).