In this paper by using Gm-C compensation technique, an ultra-low-power two-stage operational transconductance amplifier (OTA) with full rail-to-rail input/output swing is presented. The proposed configuration consists of composite transistors, improved bulk-driven folded cascode (FC) structure, feed-forward compensation path and high-speed current mirrors. In comparison with the typical FC, the proposed input stage structure has the benefit of transconductance enhancement with the same power consumption without adversely affecting the noise and offset performance. The presented OTA is simulated in 0.18 um CMOS technology and the simulation results confirm the theoretical analyses. The proposed amplifier exhibits a DC gain enhancement of 9.5 dB as well as 100 % improvement in gain-bandwidth compared to the conventional FC input stage structure. Finally, the amplifier consumes 400 nW @ 0.6 V supply voltage which makes it suitable for ultra-low-power applications.
