An Ultralow-Power Low-Voltage Class-AB Fully Differential OpAmp for Long-Life Autonomous Portable Equipment

This brief presents an ultralow-power class-AB operational amplifier (OpAmp) designed in a low-cost 0.18-
$\mu\hbox{m}$
CMOS technology. The proposed circuit uses transistors biased in the subthreshold region for low-voltage low-power operation. For a 0.8-V single supply, this OpAmp has 51-dB open-loop gain, 57-kHz unity-gain frequency, 60
$^{\circ}$
phase margin, and 65-dB common-mode rejection ratio for 8-pF loads with a power consumption of only 1.2
$\mu\hbox{W}$
. Experimental results illustrate performances such as a 0.14-
$\hbox{V}/\mu\hbox{s}$
slew rate and a 750-mV linear output swing, demonstrating its correct functionality.