Abstract— An ultra-low-voltage ultra-low-power operational transconductance amplifier (OTA) is presented in this paper. The proposed topology based on a bulk driven input differential pair. Two separate capacitors have been used for compensation of the opamp where one of them is used in a signal path and another one in a non-signal path. The circuit is designed in the 0.18µm CMOS technology. The simulation results show that the amplifier has a 84.1dB open-loop DC gain and a unity gain-bandwidth of 81 KHz while operating at 0.5V supply voltage. The total power consumption is as low as 900nW which makes it suitable for low-power bio-medical applications. Manuscript profile