  In this paper, a two-stage ultra-low-power operational amplifier is designed,
and a comparative analysis of the proposed subthreshold complementary amplifier
is presented between 180nm, 90nm, and 45nm CMOS technology. The proposed
operational amplifier is compared across several different parameters to
determine the optimal design. It achieves a maximum gain of around 75 dB and a
phase margin of 76{\deg}, dissipating just 140nW with a supply voltage of 0.5 V
which is well suited for biomedical applications that require low power and
high gain. The proposed operational amplifier has been designed using a
SPICE-based circuit simulator.
