Fully-Differential Single-Stage Class-AB Adaptive Nested Current Mirror OTA

A fully-differential single-stage class AB operational transconductance amplifier (OTA) is presented. The OTA features improved large-signal and small-signal performance due to the combined use of a non-linear current mirror and partial positive feedback at the active load. The amplifier operates in weak inversion, leading to reduced power consumption. Measurement results of a test chip prototype fabricated in a 180-nm CMOS process are presented, showing a GBW of 45 kHz and a SR of $0.23 \mathrm{V} / \mu \mathrm{s}$ for a load of 160 pF and a supply current of $1 \mu \mathrm{~A}$ drawn from $\pm 0.45 \mathrm{~V}$ power sources. The silicon area employed is just $1500 \mu^{2}$.