This paper presents a two-stage bulk-driven operational transconductance amplifier operating in weak-inversion region. The proposed amplifier is upgraded using recycling structure, current shunt technique, positive feedback source degeneration and indirect frequency compensation feedback to enhance transconductance under a reasonable stability. Combining these approaches leads to an ultra-low-power high performance amplifier without increasing power dissipation compared to the conventional one. Simulation results in 0.13-μm complementary metal–oxide–semiconductor technology show the proposed structure achieves a 63-dBDC gain at 0.25-V supply voltage with just 20-nW power dissipation.
